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POweird range value in the colorbar, matplotlib
 

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  1. POweird range value in the colorbar, matplotlib
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    <p>I am a new user to the python &amp; matplotlib, this might be a simple question but I searched the internet for hours and couldn't find a solution for this. </p> <p>I am plotting precipitation data from which is in the NetCDF format. What I find weird is that, the data doesn't have any negative values in it.(I checked that many times,just to make sure). But the value in the colorbar starts with a negative value (like -0.0000312 etc). It doesnt make sense because I dont do any manipulations to the data, other that just selecting a part of the data from the big file and plotting it. </p> <p>So my code doesn't much to it. Here is the code:</p> <pre><code>from mpl_toolkits.basemap import Basemap import numpy as np import matplotlib.pyplot as plt from netCDF4 import Dataset cd progs f=Dataset('V21_GPCP.1979-2009.nc') lats=f.variables['lat'][:] lons=f.variables['lon'][:] prec=f.variables['PREC'][:] la=lats[31:52] lo=lons[18:83] pre=prec[0,31:52,18:83] m = Basemap(width=06.e6,height=05.e6,projection='gnom',lat_0=15.,lon_0=80.) x, y = m(*np.meshgrid(lo,la)) m.drawcoastlines() m.drawmapboundary(fill_color='lightblue') m.drawparallels(np.arange(-90.,120.,5.),labels=[1,0,0,0]) m.drawmeridians(np.arange(0.,420.,5.),labels=[0,0,0,1]) cs=m.contourf(x,y,pre,50,cmap=plt.cm.jet) plt.colorbar() </code></pre> <p>The output that I got for that code was a beautiful plot, with the colorbar starting from the value -0.00001893, and the rest are positive values, and I believe are correct. Its just the minimum value thats bugging me.</p> <p>I would like to know:</p> <ol> <li>Is there anything wrong in my code? cos I know that the data is right.</li> <li>Is there a way to manually change the value to 0?</li> <li>Is it right for the values in the colorbar to change everytime we run the code, cos for the same data, the next time I run the code, the values go like this " -0.00001893, 2.00000000, 4.00000000, 6.00000000 etc"</li> <li>I want to customize them to "0.0, 2.0, 4.0, 6.0 etc"</li> </ol> <p>Thanks, Vaishu</p>
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    1. COare you really sure, that value is not right? maybe the print show a rounded value. try print pre.min()
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