Thread: [Matplotlib-users] How to plot only points which lie in a certain range

I'm sorry for this newbie question. I have a data file consisting of 3
columns, and want to plot the first versus the second column, but only if
the parameter in the third column lies in a certain range. Does somebody
have an idea how to do that?
-- 
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You need to use the numpy 'where' functionality
import numpy as np
x, y, z = np.loadtxt("fileName.dat", unpack=True) # or similar
# x, y and z are now numpy arrays and have built in functionality as 
follows:
s = (z < 10.0) & (z**2 > 0.5) # or some other constraint. Produces an 
array 's' of boolean values
plot(x[s], y[s]) # will plot only those x,y pairs for which s is True
marcusantonius <mar...@st...> 
28/10/2008 09:40 AM
To
mat...@li...
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Subject
[Matplotlib-users] How to plot only points which lie in a certain range
I'm sorry for this newbie question. I have a data file consisting of 3
columns, and want to plot the first versus the second column, but only if
the parameter in the third column lies in a certain range. Does somebody
have an idea how to do that?
-- 
View this message in context: 
http://www.nabble.com/How-to-plot-only-points-which-lie-in-a-certain-range-tp20178863p20178863.html
Sent from the matplotlib - users mailing list archive at Nabble.com.
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On Monday 27 October 2008 18:40:07 marcusantonius wrote:
> I'm sorry for this newbie question. I have a data file consisting of 3
> columns, and want to plot the first versus the second column, but only if
> the parameter in the third column lies in a certain range. Does somebody
> have an idea how to do that?
Using masked arrays ?
import numpy as np
import numpy as ma
import matplotlib.pyplot as mpl
x = ma.arange(10)
y = ma.array(np.random.rand(10))
z = ma.array(np.random.rand(10))
(z_lo, z_up) = (0.1, 0.8)
x[ (z<z_lo) | (z>z_up) ] = ma.masked
mpl.plot(x,y, 'ok-')
Alternatively,
x = ma.masked_where((z<z_lo) | (z>z_up), x)