Re: [Matplotlib-users] plotting points/locations from data file

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You may find it easier to use mlab.csv2rec or numpy.loadtxt.

e.g.

data = csv2rec(filename,delimiter=' ')
plot(data[:,0],data[:,1],'o')

On Tue, Apr 19, 2011 at 4:26 PM, Michael Rawlins <raw...@ya...>wrote:

>
> Sorry I should have mentioned that longitudes are negative; there is a '-'
> before each longitude, like so:
>
> 39.4670  -76.1670
> 46.4000  -74.7670
> 45.3830  -75.7170
> 43.6170  -79.3830
> 45.5170  -73.4170
>
>
> Also the plt.text line you sent had lon[i] rather than lons[i].  I
> corrected that and changed my longitudes to not have the '-' sign and the
> code ran without error. Could the '-' be causing a problem?  I need to input
> the lat, lon as in the file as shown above.
>
> Mike
>
>
> --- On *Tue, 4/19/11, Ian Bell <ib...@pu...>* wrote:
>
>
> From: Ian Bell <ib...@pu...>
> Subject: Re: [Matplotlib-users] plotting points/locations from data file
> To: "Michael Rawlins" <raw...@ya...>
> Cc: Mat...@li...
> Date: Tuesday, April 19, 2011, 7:22 PM
>
>
> If you want to plot a given marker at the point, for instance a circle,
> replace the last line of my code plt.text...... with
>
> plt.plot(lats,lons,'o')
>
> for a circle, or
>
> plt.plot(lats,lons,'s')
>
> for a square.  Refer to Plot<http://matplotlib.sourceforge.net/api/pyplot_api.html#matplotlib.pyplot.plot>for more information on the markers you can use.  You are getting the error
> because you have a delimiter different than a single space, so it isn't
> splitting the line.  Replace ' '  in the split command with your whitespace
> delimiter.  Is it a tab? Then you want '\t' .
>
> Good luck,
> Ian
>
> ----
> Ian Bell
> Graduate Research Assistant
> Herrick Labs
> Purdue University
> email: ib...@pu... <http://mc/compose?to=ib...@pu...>
> cell: (607)227-7626
>
>
> On Tue, Apr 19, 2011 at 7:14 PM, Michael Rawlins <raw...@ya...<http://mc/compose?to=raw...@ya...>
> > wrote:
>
>
> Yes, there is whitespace between each lat and lon on each line.  But,
> actually, I'd simply like to plot a dot at each location.  The '1' was there
> in my example because I do not yet know how to plot a particular symbol.
> Here is what I got when I tried the code you just suggested.
>
> Traceback (most recent call last):
>   File "test.py", line 319, in <module>
>
>     (lat,lon)=line.strip().split(' ')
> ValueError: too many values to unpack
>
>
> There are 203 records in the data file.  Line 319 of test.py is this:
>
>
> (lat,lon)=line.strip().split(' ')
>
>
> --- On *Tue, 4/19/11, Ian Bell <ib...@pu...<http://mc/compose?to=ib...@pu...>
> >* wrote:
>
>
> From: Ian Bell <ib...@pu... <http://mc/compose?to=ib...@pu...>>
> Subject: Re: [Matplotlib-users] plotting points/locations from data file
> To: "Michael Rawlins" <raw...@ya...<http://mc/compose?to=raw...@ya...>
> >
> Cc: Mat...@li...<http://mc/compose?to=Mat...@li...>
> Date: Tuesday, April 19, 2011, 6:52 PM
>
>
> To clarify, you are trying to read in a set of (lat,lon) points in a file
> that is space delimited, store the data, and then put a text marker at each
> point, with each point numbered in order?  The critical part is that you
> want to use a list (or numpy array) instead of a dictionary.  Something like
> this ought to do (don't have MPL on this computer though - pretty sure this
> should work):
>
> lines=open('file.txt','r').readlines()
> (lats,lons)=([],[])
> for line in lines:
>     (lat,lon)=line.strip().split(' ')
>     lats.append(float(lat))
>     lons.append(float(lon))
>
> for i in range(len(lons)):
>     plt.text(lats[i],lon[i],str(i+1),ha='center',va='center',color='white')
>
> I'm sure there are a bunch of more compact ways to do this, but this should
> work.
>
> Ian
> ----
> Ian Bell
> Graduate Research Assistant
> Herrick Labs
> Purdue University
> email: ib...@pu... <http://mc/compose?to=ib...@pu...>
> cell: (607)227-7626
>
>
> On Tue, Apr 19, 2011 at 4:09 PM, Michael Rawlins <raw...@ya...<http://mc/compose?to=raw...@ya...>
> > wrote:
>
>
> I'm trying to plot a series of points/locations on a map. I'm reading the
> latitudes and longitudes from a file, with each lat, lon pair on each record
> (line).  Here is the code:
>
> def make_float(line):
>    lati, longi = line.split()
>    return float(lati), float(longi)
>
> my_dict = {}
> with open("file.txt") as f:
>    for item in f:
>        lati,longi = make_float(item)
>        my_dict[lati] = longi
>
> xpt,ypt = m(-76.1670,39.4670 )
> plt.text(xpt,ypt,'1',color='white')
>
> #print my_dict
>
> The matplotlib code which I've previously used to plot a single point on
> the map is below, with longitude and latitude in ( ):
>
> xpt,ypt = m(-70.758392,42.960445)
> plt.text(xpt,ypt,'1',color='white')
>
> When replacing (-70.758392,42.960445) with (longi,lati), the code plots
> only a single '1' at the location of just the last coordinate pair in the
> file. So now I only need to plot them all. Does the code I've implemented
> have an implicit loop to it?
>
> Mike
>
>
>
>
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