Have to say I whole-heartedly agree with Glenn. One problem I have run into
is a funky file headers where I want to skip lines 1,2,3, and 4, but line 3
is my real header line which doesn't work so well with either of the below
solutions. I had to write my own wrapper to deal with these weird types of
files.
Ian
----
Ian Bell
Graduate Research Assistant
Herrick Labs
Purdue University
email: ib...@purdue.edu
cell: (607)227-7626
On Tue, Apr 19, 2011 at 7:32 PM, G Jones <glenn.calt...@gmail.com> wrote:
> 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 <rawlin...@yahoo.com>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...@purdue.edu>* wrote:
>>
>>
>> From: Ian Bell <ib...@purdue.edu>
>> Subject: Re: [Matplotlib-users] plotting points/locations from data file
>> To: "Michael Rawlins" <rawlin...@yahoo.com>
>> Cc: Matplotlib-users@lists.sourceforge.net
>> 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...@purdue.edu <http://mc/compose?to=ib...@purdue.edu>
>> cell: (607)227-7626
>>
>>
>> On Tue, Apr 19, 2011 at 7:14 PM, Michael Rawlins
>> <rawlin...@yahoo.com<http://mc/compose?to=rawlin...@yahoo.com>
>> > 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...@purdue.edu<http://mc/compose?to=ib...@purdue.edu>
>> >* wrote:
>>
>>
>> From: Ian Bell <ib...@purdue.edu <http://mc/compose?to=ib...@purdue.edu>>
>> Subject: Re: [Matplotlib-users] plotting points/locations from data file
>> To: "Michael Rawlins"
>> <rawlin...@yahoo.com<http://mc/compose?to=rawlin...@yahoo.com>
>> >
>> Cc:
>> Matplotlib-users@lists.sourceforge.net<http://mc/compose?to=Matplotlib-users@lists.sourceforge.net>
>> 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...@purdue.edu <http://mc/compose?to=ib...@purdue.edu>
>> cell: (607)227-7626
>>
>>
>> On Tue, Apr 19, 2011 at 4:09 PM, Michael Rawlins
>> <rawlin...@yahoo.com<http://mc/compose?to=rawlin...@yahoo.com>
>> > 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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