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[Matplotlibusers] Setting x scale manually,
but letting y scale automatic within the current xaxis
From: Pål Gunnar Ellingsen <paalge@gm...>  20120203 11:59:36
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Hi I've got a plot, containing a graph. I would like to look at certain parts of it. To do this I zoom in on the xaxis using set_xlim() Then I would like to call autoscale(axis='y') and have matplotlib autoscale the y axis within the current xaxis. I've tried several ways of doing this, both with autoscale and set_ylim(auto=True) but non of them have been able to do this, as they only autoscale y on the full graph. In the end I ended up writing my own code for calculating the new ymin and ymax ans using set_ylim([ymin, ymax]), but I feel that this should not be necessary. While googling for the a solution I found an earlier email on the matplotlib list, http://www.mailarchive.com/matplotlibusers@.../msg19664.html which describes the same problem, but was never answered. Is there any other solution for this that I've missed? Regards Pål 
From: Benjamin Root <ben.root@ou...>  20120203 14:21:57
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On Friday, February 3, 2012, Pål Gunnar Ellingsen <paalge@...> wrote: > Hi > > I've got a plot, containing a graph. > I would like to look at certain parts of it. > To do this I zoom in on the xaxis using set_xlim() > Then I would like to call autoscale(axis='y') and have matplotlib > autoscale the y axis within the current xaxis. > > I've tried several ways of doing this, both with autoscale and set_ylim(auto=True) > but non of them have been able to do this, as they only autoscale y on the full graph. > In the end I ended up writing my own code for calculating the new ymin and ymax ans using set_ylim([ymin, ymax]), > but I feel that this should not be necessary. > > While googling for the a solution I found an earlier email on the matplotlib list, > http://www.mailarchive.com/matplotlibusers@.../msg19664.html > which describes the same problem, but was never answered. > > Is there any other solution for this that I've missed? > > Regards > > Pål > Actually, the autoscaling is working as it should in your case. By default, automatic limits will encompass all data plotted. The missing piece of your puzzle is specifying an aspect constraint. ax.set_aspect() will allow for some sort of relationship between the x and y axes to exist. For example, setting it to 'equal' means that limits are chosen such that a distance on the x axis is displayed the same way as the same distance in the yaxis. There are some other preset values and I think you can specify a float as well. This is what I can remember of the top of my head. I hope this helps! Ben Root 
From: Pål Gunnar Ellingsen <paalge@gm...>  20120203 15:15:24
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Hi Thank you for trying to help me, though I can't see how aspect is going to help me. As I understand of the documentation, it would require me to know the relationship between x and y, which I don't. I can calculate it, but since it varies between each change in xlimits and different plot, it would be the same as calculating the ylimits. As for pyplot.xlim(xmin,xmax) (suggested by Ethan Swint), it does the same as ax.set_xlim() for me. Below is a sample code that will illustrate the problem. Regards Pål ####### Start code ############ #!/usr/bin/env python import matplotlib matplotlib.use('Qt4Agg') # generate postscript output by default import matplotlib.pyplot as plt import numpy as np # Creating a function to plot x = np.linspace(10, 10, 200) p = np.poly1d([2, 3, 1, 4]) y = p(x) * np.sin(x) # plotting the full figure fig = plt.figure() ax = fig.add_subplot(111) ax.plot(x, y) ax.autoscale(tight=True) plt.title('Full graph. (Press key for next plot)') plt.draw() plt.waitforbuttonpress() # This is how I'm currently doing it # x limits xmin = 2 xmax = 6 # Calculating y limits ymin = y[np.logical_and(xmin < x, x < xmax)].min() ymax = y[np.logical_and(xmin < x, x < xmax)].max() # Inserting some room room = np.maximum(np.abs(ymin * 0.05), np.abs(ymax * 0.05)) ymin = ymin + room * np.sign(ymin) ymax = ymax + room * np.sign(ymax) # Setting the limits ax.set_xlim([xmin, xmax]) ax.set_ylim([ymin, ymax]) plt.title('What I want (Press key for next plot)') plt.draw() plt.waitforbuttonpress() # This is what pyplot does by default if I only set the limits ax.autoscale(tight=True) ax.set_xlim([2, 6]) plt.title('What I get if I only use set_xlim (Press key for exit)') plt.draw() plt.waitforbuttonpress() plt.close() ####### End code ############ On 3 February 2012 15:21, Benjamin Root <ben.root@...> wrote: > > > On Friday, February 3, 2012, Pål Gunnar Ellingsen <paalge@...> > wrote: > > Hi > > > > I've got a plot, containing a graph. > > I would like to look at certain parts of it. > > To do this I zoom in on the xaxis using set_xlim() > > Then I would like to call autoscale(axis='y') and have matplotlib > > autoscale the y axis within the current xaxis. > > > > I've tried several ways of doing this, both with autoscale and > set_ylim(auto=True) > > but non of them have been able to do this, as they only autoscale y on > the full graph. > > In the end I ended up writing my own code for calculating the new ymin > and ymax ans using set_ylim([ymin, ymax]), > > but I feel that this should not be necessary. > > > > While googling for the a solution I found an earlier email on the > matplotlib list, > > > http://www.mailarchive.com/matplotlibusers@.../msg19664.html > > which describes the same problem, but was never answered. > > > > Is there any other solution for this that I've missed? > > > > Regards > > > > Pål > > > > Actually, the autoscaling is working as it should in your case. By > default, automatic limits will encompass all data plotted. > > The missing piece of your puzzle is specifying an aspect constraint. > ax.set_aspect() will allow for some sort of relationship between the x and > y axes to exist. For example, setting it to 'equal' means that limits are > chosen such that a distance on the x axis is displayed the same way as the > same distance in the yaxis. There are some other preset values and I > think you can specify a float as well. > > This is what I can remember of the top of my head. I hope this helps! > > Ben Root 
From: Benjamin Root <ben.root@ou...>  20120203 16:08:04
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On Fri, Feb 3, 2012 at 9:15 AM, Pål Gunnar Ellingsen <paalge@...>wrote: > Hi > > Thank you for trying to help me, though I can't see how aspect is going > to help me. As I understand of the documentation, it would require me to > know the > relationship between x and y, which I don't. > I can calculate it, but since it varies between each change in xlimits > and different plot, it would be the same as calculating the ylimits. > > As for pyplot.xlim(xmin,xmax) (suggested by Ethan Swint), it does the same > as ax.set_xlim() for me. > > Below is a sample code that will illustrate the problem. > > Regards > > Pål > > ####### Start code ############ > > #!/usr/bin/env python > import matplotlib > matplotlib.use('Qt4Agg') # generate postscript output by default > > import matplotlib.pyplot as plt > import numpy as np > > # Creating a function to plot > x = np.linspace(10, 10, 200) > p = np.poly1d([2, 3, 1, 4]) > y = p(x) * np.sin(x) > > # plotting the full figure > fig = plt.figure() > > ax = fig.add_subplot(111) > ax.plot(x, y) > ax.autoscale(tight=True) > plt.title('Full graph. (Press key for next plot)') > plt.draw() > > plt.waitforbuttonpress() > > # This is how I'm currently doing it > # x limits > xmin = 2 > xmax = 6 > > # Calculating y limits > ymin = y[np.logical_and(xmin < x, x < xmax)].min() > ymax = y[np.logical_and(xmin < x, x < xmax)].max() > > # Inserting some room > room = np.maximum(np.abs(ymin * 0.05), np.abs(ymax * 0.05)) > ymin = ymin + room * np.sign(ymin) > ymax = ymax + room * np.sign(ymax) > > # Setting the limits > ax.set_xlim([xmin, xmax]) > ax.set_ylim([ymin, ymax]) > > plt.title('What I want (Press key for next plot)') > plt.draw() > plt.waitforbuttonpress() > > # This is what pyplot does by default if I only set the limits > ax.autoscale(tight=True) > ax.set_xlim([2, 6]) > > plt.title('What I get if I only use set_xlim (Press key for exit)') > plt.draw() > plt.waitforbuttonpress() > plt.close() > > ####### End code ############ > > > Ok, I see what you want. You want the ylimits to automatically change to fit only the data that is displayed for the xdomain you have chosen. I have tried some tricks, and I am not sure that it is currently possible. There might even be some sort of bug at play here because the function ax.update_datalim() does not appear to update the internal data used for autoscaling. We might have to look into this further. Ben Root 
From: Pål Gunnar Ellingsen <paalge@gm...>  20120203 16:49:55
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Hi Yes you've understood my problem correctly. Let me know if there is anything I can do to help solve this issue. Regards Pål On 3 February 2012 17:07, Benjamin Root <ben.root@...> wrote: > > > On Fri, Feb 3, 2012 at 9:15 AM, Pål Gunnar Ellingsen <paalge@...>wrote: > >> Hi >> >> Thank you for trying to help me, though I can't see how aspect is going >> to help me. As I understand of the documentation, it would require me to >> know the >> relationship between x and y, which I don't. >> I can calculate it, but since it varies between each change in xlimits >> and different plot, it would be the same as calculating the ylimits. >> >> As for pyplot.xlim(xmin,xmax) (suggested by Ethan Swint), it does the >> same as ax.set_xlim() for me. >> >> Below is a sample code that will illustrate the problem. >> >> Regards >> >> Pål >> >> ####### Start code ############ >> >> #!/usr/bin/env python >> import matplotlib >> matplotlib.use('Qt4Agg') # generate postscript output by default >> >> import matplotlib.pyplot as plt >> import numpy as np >> >> # Creating a function to plot >> x = np.linspace(10, 10, 200) >> p = np.poly1d([2, 3, 1, 4]) >> y = p(x) * np.sin(x) >> >> # plotting the full figure >> fig = plt.figure() >> >> ax = fig.add_subplot(111) >> ax.plot(x, y) >> ax.autoscale(tight=True) >> plt.title('Full graph. (Press key for next plot)') >> plt.draw() >> >> plt.waitforbuttonpress() >> >> # This is how I'm currently doing it >> # x limits >> xmin = 2 >> xmax = 6 >> >> # Calculating y limits >> ymin = y[np.logical_and(xmin < x, x < xmax)].min() >> ymax = y[np.logical_and(xmin < x, x < xmax)].max() >> >> # Inserting some room >> room = np.maximum(np.abs(ymin * 0.05), np.abs(ymax * 0.05)) >> ymin = ymin + room * np.sign(ymin) >> ymax = ymax + room * np.sign(ymax) >> >> # Setting the limits >> ax.set_xlim([xmin, xmax]) >> ax.set_ylim([ymin, ymax]) >> >> plt.title('What I want (Press key for next plot)') >> plt.draw() >> plt.waitforbuttonpress() >> >> # This is what pyplot does by default if I only set the limits >> ax.autoscale(tight=True) >> ax.set_xlim([2, 6]) >> >> plt.title('What I get if I only use set_xlim (Press key for exit)') >> plt.draw() >> plt.waitforbuttonpress() >> plt.close() >> >> ####### End code ############ >> >> >> > Ok, I see what you want. You want the ylimits to automatically change to > fit only the data that is displayed for the xdomain you have chosen. > > I have tried some tricks, and I am not sure that it is currently > possible. There might even be some sort of bug at play here because the > function ax.update_datalim() does not appear to update the internal data > used for autoscaling. We might have to look into this further. > > Ben Root > > 
From: Eric Firing <efiring@ha...>  20120203 18:56:50

On 02/03/2012 06:07 AM, Benjamin Root wrote: > > > On Fri, Feb 3, 2012 at 9:15 AM, Pål Gunnar Ellingsen <paalge@... > <mailto:paalge@...>> wrote: > > Hi > > Thank you for trying to help me, though I can't see how aspect is going > to help me. As I understand of the documentation, it would require > me to know the > relationship between x and y, which I don't. > I can calculate it, but since it varies between each change in xlimits > and different plot, it would be the same as calculating the ylimits. > > As for pyplot.xlim(xmin,xmax) (suggested by Ethan Swint), it does > the same as ax.set_xlim() for me. > > Below is a sample code that will illustrate the problem. > > Regards > > Pål > > ####### Start code ############ > > #!/usr/bin/env python > import matplotlib > matplotlib.use('Qt4Agg') # generate postscript output by default > > import matplotlib.pyplot as plt > import numpy as np > > # Creating a function to plot > x = np.linspace(10, 10, 200) > p = np.poly1d([2, 3, 1, 4]) > y = p(x) * np.sin(x) > > # plotting the full figure > fig = plt.figure() > > ax = fig.add_subplot(111) > ax.plot(x, y) > ax.autoscale(tight=True) > plt.title('Full graph. (Press key for next plot)') > plt.draw() > > plt.waitforbuttonpress() > > # This is how I'm currently doing it > # x limits > xmin = 2 > xmax = 6 > > # Calculating y limits > ymin = y[np.logical_and(xmin < x, x < xmax)].min() > ymax = y[np.logical_and(xmin < x, x < xmax)].max() > > # Inserting some room > room = np.maximum(np.abs(ymin * 0.05), np.abs(ymax * 0.05)) > ymin = ymin + room * np.sign(ymin) > ymax = ymax + room * np.sign(ymax) > > # Setting the limits > ax.set_xlim([xmin, xmax]) > ax.set_ylim([ymin, ymax]) > > plt.title('What I want (Press key for next plot)') > plt.draw() > plt.waitforbuttonpress() > > # This is what pyplot does by default if I only set the limits > ax.autoscale(tight=True) > ax.set_xlim([2, 6]) > > plt.title('What I get if I only use set_xlim (Press key for exit)') > plt.draw() > plt.waitforbuttonpress() > plt.close() > > ####### End code ############ > > > > Ok, I see what you want. You want the ylimits to automatically change > to fit only the data that is displayed for the xdomain you have chosen. This has never been supported; it would have to be a new option. I suspect it would be quite difficult to get this right in general, even though the concept seems simple enough. Eric > > I have tried some tricks, and I am not sure that it is currently > possible. There might even be some sort of bug at play here because the > function ax.update_datalim() does not appear to update the internal data > used for autoscaling. We might have to look into this further. > > Ben Root > > > >  > Try before you buy = See our experts in action! > The most comprehensive online learning library for Microsoft developers > is just $99.99! Visual Studio, SharePoint, SQL  plus HTML5, CSS3, MVC3, > Metro Style Apps, more. Free future releases when you subscribe now! > http://p.sf.net/sfu/learndevnowdev2 > > > > _______________________________________________ > Matplotlibusers mailing list > Matplotlibusers@... > https://lists.sourceforge.net/lists/listinfo/matplotlibusers 
From: Pål Gunnar Ellingsen <paalge@gm...>  20120206 10:47:40
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Hi I understand that it would be hard to implement, as it requires that all the points are checked, which for a arbitrary plot is not easy. Though is this not what is already done for the normal autoscale, or have I misunderstood how the normal autoscale is done? I would like to have this as a new feature, as it would prove useful for analysing graphs, especially in scientific research. Kind regards Pål On 3 February 2012 19:56, Eric Firing <efiring@...> wrote: > On 02/03/2012 06:07 AM, Benjamin Root wrote: > > > > > > On Fri, Feb 3, 2012 at 9:15 AM, Pål Gunnar Ellingsen <paalge@... > > <mailto:paalge@...>> wrote: > > > > Hi > > > > Thank you for trying to help me, though I can't see how aspect is > going > > to help me. As I understand of the documentation, it would require > > me to know the > > relationship between x and y, which I don't. > > I can calculate it, but since it varies between each change in > xlimits > > and different plot, it would be the same as calculating the ylimits. > > > > As for pyplot.xlim(xmin,xmax) (suggested by Ethan Swint), it does > > the same as ax.set_xlim() for me. > > > > Below is a sample code that will illustrate the problem. > > > > Regards > > > > Pål > > > > ####### Start code ############ > > > > #!/usr/bin/env python > > import matplotlib > > matplotlib.use('Qt4Agg') # generate postscript output by default > > > > import matplotlib.pyplot as plt > > import numpy as np > > > > # Creating a function to plot > > x = np.linspace(10, 10, 200) > > p = np.poly1d([2, 3, 1, 4]) > > y = p(x) * np.sin(x) > > > > # plotting the full figure > > fig = plt.figure() > > > > ax = fig.add_subplot(111) > > ax.plot(x, y) > > ax.autoscale(tight=True) > > plt.title('Full graph. (Press key for next plot)') > > plt.draw() > > > > plt.waitforbuttonpress() > > > > # This is how I'm currently doing it > > # x limits > > xmin = 2 > > xmax = 6 > > > > # Calculating y limits > > ymin = y[np.logical_and(xmin < x, x < xmax)].min() > > ymax = y[np.logical_and(xmin < x, x < xmax)].max() > > > > # Inserting some room > > room = np.maximum(np.abs(ymin * 0.05), np.abs(ymax * 0.05)) > > ymin = ymin + room * np.sign(ymin) > > ymax = ymax + room * np.sign(ymax) > > > > # Setting the limits > > ax.set_xlim([xmin, xmax]) > > ax.set_ylim([ymin, ymax]) > > > > plt.title('What I want (Press key for next plot)') > > plt.draw() > > plt.waitforbuttonpress() > > > > # This is what pyplot does by default if I only set the limits > > ax.autoscale(tight=True) > > ax.set_xlim([2, 6]) > > > > plt.title('What I get if I only use set_xlim (Press key for exit)') > > plt.draw() > > plt.waitforbuttonpress() > > plt.close() > > > > ####### End code ############ > > > > > > > > Ok, I see what you want. You want the ylimits to automatically change > > to fit only the data that is displayed for the xdomain you have chosen. > > This has never been supported; it would have to be a new option. I > suspect it would be quite difficult to get this right in general, even > though the concept seems simple enough. > > Eric > > > > > I have tried some tricks, and I am not sure that it is currently > > possible. There might even be some sort of bug at play here because the > > function ax.update_datalim() does not appear to update the internal data > > used for autoscaling. We might have to look into this further. > > > > Ben Root > > > > > > > > >  > > Try before you buy = See our experts in action! > > The most comprehensive online learning library for Microsoft developers > > is just $99.99! Visual Studio, SharePoint, SQL  plus HTML5, CSS3, MVC3, > > Metro Style Apps, more. Free future releases when you subscribe now! > > http://p.sf.net/sfu/learndevnowdev2 > > > > > > > > _______________________________________________ > > Matplotlibusers mailing list > > Matplotlibusers@... > > https://lists.sourceforge.net/lists/listinfo/matplotlibusers > > > > >  > Try before you buy = See our experts in action! > The most comprehensive online learning library for Microsoft developers > is just $99.99! Visual Studio, SharePoint, SQL  plus HTML5, CSS3, MVC3, > Metro Style Apps, more. Free future releases when you subscribe now! > http://p.sf.net/sfu/learndevnowdev2 > _______________________________________________ > Matplotlibusers mailing list > Matplotlibusers@... > https://lists.sourceforge.net/lists/listinfo/matplotlibusers > 
From: Benjamin Root <ben.root@ou...>  20120206 17:03:13
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On Mon, Feb 6, 2012 at 4:47 AM, Pål Gunnar Ellingsen <paalge@...>wrote: > Hi > > I understand that it would be hard to implement, as it requires that all > the points are checked, which for a arbitrary plot is not easy. > Though is this not what is already done for the normal autoscale, or have > I misunderstood how the normal autoscale is done? > > I would like to have this as a new feature, as it would prove useful for > analysing graphs, especially in scientific research. > > Kind regards > > Pål > > > Pal, Normal autoscaling (when aspect is None, which is default) means to display all the data that has been plotted. This is possible because the plotting functions (which were given the data as input) updates the limits of the "known data bounding box" for the axes. This data is not stored except within each artist object, in their own form. It becomes difficult to then "requery" that data in the general case. It isn't to say that it isn't possible to do, just that the architecture isn't set up to query subsets of collections. I hope this is clearer, Ben Root 
From: Pål Gunnar Ellingsen <paalge@gm...>  20120206 17:15:29
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Hi That was a very nice explanation of how autoscale works, thank you very much :D After now understanding how the function autoscale function works, I see that this would be a major change in the code, as it would require the axes to know all of the bounding boxes, and not only one of them. As it, at least in my code, is easy to calculate the new limits on the unset axis, I would not put this up as something that should be a feature. Though I think the documentation for autoscale, section axis could be a bit clearer and state that autoscaling only one axis autoscales that axis with respect to everything plotted, even though xlim/ylim has been set. Regards Pål On 6 February 2012 18:02, Benjamin Root <ben.root@...> wrote: > > > On Mon, Feb 6, 2012 at 4:47 AM, Pål Gunnar Ellingsen <paalge@...>wrote: > >> Hi >> >> I understand that it would be hard to implement, as it requires that all >> the points are checked, which for a arbitrary plot is not easy. >> Though is this not what is already done for the normal autoscale, or have >> I misunderstood how the normal autoscale is done? >> >> I would like to have this as a new feature, as it would prove useful for >> analysing graphs, especially in scientific research. >> >> Kind regards >> >> Pål >> >> >> > Pal, > > Normal autoscaling (when aspect is None, which is default) means to > display all the data that has been plotted. This is possible because the > plotting functions (which were given the data as input) updates the limits > of the "known data bounding box" for the axes. This data is not stored > except within each artist object, in their own form. It becomes difficult > to then "requery" that data in the general case. It isn't to say that it > isn't possible to do, just that the architecture isn't set up to query > subsets of collections. > > I hope this is clearer, > Ben Root > > 