De Pauw Antoine wrote:
> Hi Jeff,
>
> I have put the code online with a sample of the data here:
>
> http://snipplr.com/view/8307/map-plotting-python-code-temporary/
>
> I hope you'll be able to give me some advice as it is quite difficult for
> someone new in python and scientific computation
>
> Antoine De Pauw
> Collaborateur de recherches, Informatique - Research collaborator, IT
> Laboratoire de chimie quantique et photophysique - Quantum chemistry and
> photophysics laboratory
> Université Libre de Bruxelles - ULB
>
Antoine: I may have the size of the pixels wrong, and lat/lon
transposed, but this is the general idea:
from mpl_toolkits.basemap import Basemap
import matplotlib.pyplot as plt
import numpy as np
lats = []; lons = []; data = []
for line in open('pixels.dat'):
linesplit = line.split(',')
lons.append(float(linesplit[1]))
lats.append(float(linesplit[0]))
data.append(float(linesplit[2]))
map =
Basemap(projection='mill',llcrnrlat=min(lats)-5,urcrnrlat=max(lats)+5,\
urcrnrlon=max(lons)+5,llcrnrlon=min(lons)-5,resolution='l')
x,y = map(lons,lats)
plt.scatter(x,y,s=25,c=data,marker='s',edgecolor="None",cmap=plt.cm.jet)
plt.colorbar(shrink=0.6)
map.drawcoastlines()
plt.show()
-Jeff
> -----Original Message-----
> From: Jeff Whitaker [mailto:[EMAIL PROTECTED]
> Sent: mercredi 10 septembre 2008 16:45
> To: Antoine De Pauw
> Cc: Matplotlib Users
> Subject: Re: Information request
>
> Antoine De Pauw wrote:
>
>> Thanks Jeff,
>>
>> In fact my points are arranged in three unsorted arrays, with a simple
>>
> scheme (thats why I couldn't plot them with imshow and others)
>
>> arrays:
>>
>> [lat][lon][val]
>> [-10][ 17][0.3]
>> [ 37][ 23][3.7]
>> ... ... ...
>>
>> and so for many rows...
>>
>> what I have to do is looping through my arrays like that
>>
>> while i < rowcount:
>> plot_to_map(lat[i],lon[i],val[i])
>>
>> it is evidently an idea of how it could be done easily but my knowledge of
>>
> these libraries is too weak for me to figure out how to do it
>
>> my data comes from huge binary files but is extremely simple, so it would
>>
> be really easy for anyone to help me as the problem itself is how to put
> unsorted points on the map with latitude and longitude coordinates
>
>
> Antoine: You haven't said if your data forms a rectangular array. If
> so, you can build a 2-d array from the input file and plot it with
> imshow. If not, you can still plug the elements into a 2-d masked
> array, leaving the missing pixels masked. You say the points are
> 'unsorted', does that mean they are randomly distributed and do not form
> a rectangular grid?
>
> It would really be much easier to help if you gave us more information,
> such as how the data is structured, what the pixel footprint is, etc.
> Perhaps you could post the binary file on an ftp site somewhere with
> code to read it.
>
> Also, please hit 'reply all' when replying, so the matplotlib users
> mailing list is CC'ed.
>
> -Jeff
>
>>> Antoine De Pauw wrote:
>>>
>>>> Sir,
>>>>
>>>> I'm sorry, as english is not my mothertongue and it is sometimes
>>>>
> difficult to be understandable.
>
>>>> All is in the script I gave to you initially, except the point drawing
>>>>
> code which would be useless as it is proven not to work (I dont know the
> method to do it).
>
>>>> What I have is a map, and a set of pixels I have to put on it with
>>>>
> geographic coordinates.
>
>>>> I cannot find the right method to put colour pixels on the map, that's
>>>>
> the problem.
>
>>>> I have that map in miller projection, and three arrays containing
>>>>
> respectively latitude, longitude and satellite measured value.
>
>>>> What I need to obtain is something approximately like this:
>>>>
> http://www.oma.be/BIRA-IASB/Molecules/SO2archive/info/background/so2sc200703
> _00_lr.gif but with the basemap toolkit.
>
>>>> So, my question is: how could I do to plot a coloured pixel at
>>>>
> coordinates lat:lon on that map? If I have just the method to project a
> geographic coordinate on the map and put a coloured pixel at the right
> place, all is done and I just have to loop my arrays... Also, I would have
> to implement some antialiasing on the map.
>
>>>>
>>>>
>>> Antoine:
>>>
>>> Are the pixels arranged on a regular grid - or are they randomly
>>> distributed? If they are on a grid, it's easy (using pcolor or imshow).
>>>
>>> If you could send me your data I may be able to get you started.
>>>
>>> (I'm cc'ing the matplotlib list so others can join in the discussion).
>>>
>>>
>>> -Jeff
>>>
>>>> If this is not possible to do it in a simple and explainable way, please
>>>>
> tell me and I'll continue using matlab or searching for the bit of code
> which will save me
>
>>>> Anyway, I have to thank you for your interest to help me..
>>>>
>>>> Many thanks,
>>>>
>>>> Antoine De Pauw
>>>>
>>>>
>>>>
>>>>> Antoine De Pauw wrote:
>>>>>
>>>>>
>>>>>> Hi, and thanks for the answer
>>>>>>
>>>>>> In fact, what I do is reading a binary file to obtain 3 arrays
>>>>>>
> (Lat,Lon,Val) describing geographic points which are associated by index
> (like point 1 is Lat[0]:Lon[0] with value Val[0])
>
>>>>>> What I need to do is to plot some points on the map (miller projection
>>>>>>
> for most) based on latitude and longitude, to obtain a colour map (points
> are unordered, it is from IASI satellite computations)
>
>>>>>> I'm able to create a map, draw simple things on it, etc but the
>>>>>>
> problem I have is any method I try for plotting points is failing, either
> pcolor, pcolormesh, imshow, etc.
>
>>>>>> When I found your post on that mailing list, I figured out that you
>>>>>>
> might have the experience and skills to easily explain to me how to
> manipulate these points and plot them on the map, as there's like no help on
> the web except standard examples...
>
>>>>>> Please tell me if this is possible for you to give me some tips, or if
>>>>>>
> it takes too much of your time just advice me some lectures
>
>>>>>> Best regards,
>>>>>>
>>>>>> De Pauw Antoine
>>>>>>
>>>>>>
>>>>>>
>>>>> Antoine: It would really help to have a script demonstrating your
>>>>> problem. It sounds to me like you want to plot markers representing a
>>>>> set of points - for that you should use the scatter method. pcolor,
>>>>> pcolormesh and friends are for plotting gridded data.
>>>>>
>>>>> -Jeff
>>>>>
>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>> De Pauw Antoine wrote:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>> Dear sir,
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> I’m currently trying to improve our plotting tools here at the
>>>>>>>>
> “Quantum
>
>>>>>>>> Chemistry and Photophysics” section of the Université Libre de
>>>>>>>>
>
>
>>>>>>>> Bruxelles, and I ran, after many time passed at searching for a
>>>>>>>> solution, on an explanation from you here:
>>>>>>>>
>>>>>>>>
> http://www.nabble.com/Re:-matplotlib-basemap-question-tt17759370.html
>
>>>>>>>>
>>>>>>>>
>>>>>>>> It seems that you could help me find a solution, as I cannot plot
>>>>>>>>
> any
>
>>>>>>>> points on maps.
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> Could you please tell me what I could do to plot data in a simple
>>>>>>>>
> way,
>
>>>>>>>> assuming I have 3 unordered arrays containing respectively latitude,
>>>>>>>>
>
>
>>>>>>>> longitude and values to plot?
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> Some tips would be very nice from you as any method I have tried so
>>>>>>>>
> far
>
>>>>>>>> give me some errors…
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> Thank you very much in advance,
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> Best regards,
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> PS: I give you the code I’m using currently, missing the
>>>>>>>>
> plotting part
>
>>>>>>>>
>>>>>>>>
>>>>>>>> from mpl_toolkits.basemap import Basemap
>>>>>>>>
>>>>>>>> from numpy import *
>>>>>>>>
>>>>>>>> from scipy.io.numpyio import fread
>>>>>>>>
>>>>>>>> import matplotlib.pyplot as plt
>>>>>>>>
>>>>>>>> import numpy as np
>>>>>>>>
>>>>>>>> import os
>>>>>>>>
>>>>>>>> import sys
>>>>>>>>
>>>>>>>> import array
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> fileName="c:/20080821.b56"
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> print('preparing map')
>>>>>>>>
>>>>>>>> map =
>>>>>>>>
>>>>>>>>
> Basemap(projection='mill',lat_0=0,lon_0=0,resolution='i',area_thresh=30000.)
>
>>>>>>>> map.drawcoastlines(0.5,antialiased=1)
>>>>>>>>
>>>>>>>> map.drawmapboundary()
>>>>>>>>
>>>>>>>> #map.drawmeridians(np.arange(-180,180,60),linewidth=0.5,
>>>>>>>> labels=np.arange(-180,180,60), labelstyle="+/-")
>>>>>>>>
>>>>>>>> #map.drawparallels(np.arange(-90,90,30), linewidth=0.5,
>>>>>>>> labels=np.arange(-180,180,30), labelstyle="+/-")
>>>>>>>>
>>>>>>>> print('reading binary data')
>>>>>>>>
>>>>>>>> nbreligne=long(os.stat(fileName)[6])/(8*int(fileName[-2:]))
>>>>>>>>
>>>>>>>> Lat=zeros(nbreligne)
>>>>>>>>
>>>>>>>> Lon=zeros(nbreligne)
>>>>>>>>
>>>>>>>> Val=zeros(nbreligne)
>>>>>>>>
>>>>>>>> rawfile=fromfile(open(fileName,'rb'),'d',-1)
>>>>>>>>
>>>>>>>> Lat=rawfile[0:nbreligne]
>>>>>>>>
>>>>>>>> Lon=rawfile[nbreligne:nbreligne*2]
>>>>>>>>
>>>>>>>> Val=rawfile[nbreligne*21:nbreligne*22]
>>>>>>>>
>>>>>>>> print('shifting latitudes and projecting to map')
>>>>>>>>
>>>>>>>> i=0
>>>>>>>>
>>>>>>>> while i < nbreligne:
>>>>>>>>
>>>>>>>> if(Lon[i]>180):
>>>>>>>>
>>>>>>>> print(Lon[i])
>>>>>>>>
>>>>>>>> Lon[i]-=360
>>>>>>>>
>>>>>>>> print(Lon[i])
>>>>>>>>
>>>>>>>> i+=1
>>>>>>>>
>>>>>>>> print('plotting data')
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> #plotting code comes here
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>> Antoine: If you send me a self-contained script that produces the
>>>>>>> problem you see, I can help you debug it. As it stands now, I have
>>>>>>>
> very
>
>>>>>>> little to work with - it could be your plotting commands, or it could
>>>>>>>
> be
>
>>>>>>> your data.
>>>>>>>
>>>>>>> -Jeff
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> print('saving map')
>>>>>>>>
>>>>>>>> plt.savefig("testfig.png",dpi=600)
>>>>>>>>
>>>>>>>> print('done')
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> *Antoine De Pauw*
>>>>>>>> Collaborateur de recherches, Informatique - Research collaborator,
>>>>>>>>
> IT
>
>>>>>>>> Laboratoire de chimie quantique et photophysique - Quantum chemistry
>>>>>>>>
> and
>
>>>>>>>> photophysics laboratory
>>>>>>>> *Université Libre de Bruxelles - ULB <http://ww.ulb.ac.be/>*
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>> --
>>>>>>> Jeffrey S. Whitaker Phone : (303)497-6313
>>>>>>> Meteorologist FAX : (303)497-6449
>>>>>>> NOAA/OAR/PSD R/PSD1 Email : [EMAIL PROTECTED]
>>>>>>> 325 Broadway Office : Skaggs Research Cntr 1D-113
>>>>>>> Boulder, CO, USA 80303-3328 Web : http://tinyurl.com/5telg
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>> --
>>>>> Jeffrey S. Whitaker Phone : (303)497-6313
>>>>> NOAA/OAR/CDC R/PSD1 FAX : (303)497-6449
>>>>> 325 Broadway Boulder, CO, USA 80305-3328
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>> --
>>> Jeffrey S. Whitaker Phone : (303)497-6313
>>> NOAA/OAR/CDC R/PSD1 FAX : (303)497-6449
>>> 325 Broadway Boulder, CO, USA 80305-3328
>>>
>>>
>>>
>>>
>>
>
>
>
--
Jeffrey S. Whitaker Phone : (303)497-6313
NOAA/OAR/CDC R/PSD1 FAX : (303)497-6449
325 Broadway Boulder, CO, USA 80305-3328
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