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From: Ryan Krauss <ryanlists@gm...>  20090515 23:51:24

From: Ryan Krauss <ryanlists@gm...>  20090515 23:52:51
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Oh, and in case it matters I am running In [36]: matplotlib.__version__ Out[36]: '0.98.5.2' on Ubuntu 9.04 (with the rather lame name of Jaunty Jackolope). On Fri, May 15, 2009 at 6:51 PM, Ryan Krauss <ryanlists@...> wrote: > I think I used to use plot with linestyle='steps' to plot data for > zeroorder hold control systems. This means that if the system is updating > on a period of 0.01 seconds (100 Hz), the values should be considered held > from 0 to 0.0099999999999999 and then from 0.01 to 0.01999999999 and so on > each time step. So, what I want is a plot that looks like late_steps.png > (hopefully attached), but what I am currently getting is early_steps.png. > > This code snippet recreates my problem. My t2 hack almost makes the plot > look right. > > t = arange(0,0.1,0.01) > y = 10*t > clf() > plot(t,y,linestyle='steps') > plot(t,y,'o') > savefig('early_steps.png') > > t2 = t+0.01 > clf() > plot(t2,y,linestyle='steps') > plot(t,y,'o') > savefig('late_steps.png') > > > > Is this a bug, is this the expected behavior for other applications, or can > this be changed with some configuration setting? > > Thanks, > > Ryan > 
From: Ryan Krauss <ryanlists@gm...>  20090515 23:59:42
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RTFM: plot(t,y, drawstyle='stepspost') This was really helpful: http://matplotlib.sourceforge.net/examples/pylab_examples/set_and_get.html especially >>> line, = plot([1,2,3]) >>> setp(line, linestyle='') On Fri, May 15, 2009 at 6:52 PM, Ryan Krauss <ryanlists@...> wrote: > Oh, and in case it matters I am running > > In [36]: matplotlib.__version__ > Out[36]: '0.98.5.2' > > on Ubuntu 9.04 (with the rather lame name of Jaunty Jackolope). > > > On Fri, May 15, 2009 at 6:51 PM, Ryan Krauss <ryanlists@...> wrote: > >> I think I used to use plot with linestyle='steps' to plot data for >> zeroorder hold control systems. This means that if the system is updating >> on a period of 0.01 seconds (100 Hz), the values should be considered held >> from 0 to 0.0099999999999999 and then from 0.01 to 0.01999999999 and so on >> each time step. So, what I want is a plot that looks like late_steps.png >> (hopefully attached), but what I am currently getting is early_steps.png. >> >> This code snippet recreates my problem. My t2 hack almost makes the plot >> look right. >> >> t = arange(0,0.1,0.01) >> y = 10*t >> clf() >> plot(t,y,linestyle='steps') >> plot(t,y,'o') >> savefig('early_steps.png') >> >> t2 = t+0.01 >> clf() >> plot(t2,y,linestyle='steps') >> plot(t,y,'o') >> savefig('late_steps.png') >> >> >> >> Is this a bug, is this the expected behavior for other applications, or >> can this be changed with some configuration setting? >> >> Thanks, >> >> Ryan >> > > 
From: Paul Ray <Paul.Ray@nr...>  20090717 22:15:59

Ryan Krauss2 wrote: > > RTFM: > > plot(t,y, drawstyle='stepspost') > > Actually, 'stepspre' (which is the default) and 'stepspost' seem to have swapped definitions. Here is what the docs say: *where*: [ 'pre'  'post'  'mid' ] If 'pre', the interval from x[i] to x[i+1] has level y[i] If 'post', that interval has level y[i+1] If 'mid', the jumps in *y* occur halfway between the *x*values. In fact both the default behavior and what you get with stepspre are what SHOULD happen with stepspost. And stepspost (as you point out) does what should be the default behavior and that of stepspre. I have filed a bug report on this, since it is very important that this work as expected. As the original poster pointed out, this used to work correctly but recently seems to have gotten broken. Cheers,  Paul  View this message in context: http://www.nabble.com/possiblebugwithlinestyle%3D%27steps%27tp23568959p24542440.html Sent from the matplotlib  users mailing list archive at Nabble.com. 
From: John Hunter <jdh2358@gm...>  20090719 13:43:22

On Fri, Jul 17, 2009 at 5:15 PM, Paul Ray<Paul.Ray@...> wrote: > > > Ryan Krauss2 wrote: >> >> RTFM: >> >> plot(t,y, drawstyle='stepspost') >> >> > > Actually, 'stepspre' (which is the default) and 'stepspost' seem to have > swapped definitions. > Here is what the docs say: > *where*: [ 'pre'  'post'  'mid' ] > If 'pre', the interval from x[i] to x[i+1] has level y[i] > If 'post', that interval has level y[i+1] > If 'mid', the jumps in *y* occur halfway between the > *x*values. > > In fact both the default behavior and what you get with stepspre are what > SHOULD happen with stepspost. And stepspost (as you point out) does what > should be the default behavior and that of stepspre. > > I have filed a bug report on this, since it is very important that this work > as expected. As the original poster pointed out, this used to work > correctly but recently seems to have gotten broken. I am looking first at the behavior of plot with the drawstyle property set  let's make sure this is correct before turning to the steps command, which just uses plot with the drawstyle set  here is my test code import numpy as np import matplotlib.pyplot as plt fig = plt.figure() ax = fig.add_subplot(111) a = np.array([1,2,3,4,5]) styles = 'default' , 'steps' , 'stepspre' , 'stepsmid' , 'stepspost' styles = 'steps' , 'stepspre' for ls in styles: ax.plot(a, ls=ls, label=ls, lw=2) ax.legend(loc='upper left') plt.show() pre causes the step to rise on the x[i], post causes it to rise on x[i+1] and mid in the middle. This seems like the correct behavior. So it does look like the docstring for 'step' is incorrect, and I've changed it to read *where*: [ 'pre'  'post'  'mid' ] If 'pre', the interval from x[i] to x[i+1] has level y[i+1] If 'post', that interval has level y[i] If 'mid', the jumps in *y* occur halfway between the JDH 
From: Paul Ray <Paul.Ray@nr...>  20090825 20:41:02

Hi, I just installed matplotlib 0.99.0 and I see that this problem is still there. The command plot(a,ls='steps') is equivalent to plot(a,ls='stepspre') and both cause the first value of the array to NOT be plotted. This is REALLY not what should happen when one plots an array with several values. It is fine if there is a custom option to make that behavior (like 'stepspre'), but the default for ls='steps' or step(x,y) must be to have the first flat level at the level of the first entry (what the 'stepspost' does). The docstring now correctly describes the behavior, so that is good, but please please make the default "steps" be "stepspost". Thanks,  Paul On Jul 19, 2009, at 9:35 AM, John Hunter wrote: > On Fri, Jul 17, 2009 at 5:15 PM, Paul Ray<Paul.Ray@...> > wrote: >> >> >> Ryan Krauss2 wrote: >>> >>> RTFM: >>> >>> plot(t,y, drawstyle='stepspost') >>> >>> >> >> Actually, 'stepspre' (which is the default) and 'stepspost' seem >> to have >> swapped definitions. >> Here is what the docs say: >> *where*: [ 'pre'  'post'  'mid' ] >> If 'pre', the interval from x[i] to x[i+1] has level y[i] >> If 'post', that interval has level y[i+1] >> If 'mid', the jumps in *y* occur halfway between the >> *x*values. >> >> In fact both the default behavior and what you get with stepspre >> are what >> SHOULD happen with stepspost. And stepspost (as you point out) >> does what >> should be the default behavior and that of stepspre. >> >> I have filed a bug report on this, since it is very important that >> this work >> as expected. As the original poster pointed out, this used to work >> correctly but recently seems to have gotten broken. > > > > I am looking first at the behavior of plot with the drawstyle property > set  let's make sure this is correct before turning to the steps > command, which just uses plot with the drawstyle set  here is my > test code > > import numpy as np > import matplotlib.pyplot as plt > > fig = plt.figure() > ax = fig.add_subplot(111) > > a = np.array([1,2,3,4,5]) > > styles = 'default' , 'steps' , 'stepspre' , 'stepsmid' , 'steps > post' > styles = 'steps' , 'stepspre' > for ls in styles: > ax.plot(a, ls=ls, label=ls, lw=2) > > ax.legend(loc='upper left') > > plt.show() > > > pre causes the step to rise on the x[i], post causes it to rise on > x[i+1] and mid in the middle. This seems like the correct behavior. > So it does look like the docstring for 'step' is incorrect, and I've > changed it to read > > > *where*: [ 'pre'  'post'  'mid' ] > If 'pre', the interval from x[i] to x[i+1] has level y[i+1] > > If 'post', that interval has level y[i] > > If 'mid', the jumps in *y* occur halfway between the > > > JDH 