subtracting arrays in numpy and plotting with pylab

Question

I have a simple text file composed of 8 columns and I read it with loadtxt function. I want to plot as x-axis column6-column7 and as y-axis column7-column8 so I put this command

>>> pl.plot(np.subtract(data2[:,6], data2[:7]), np.subtract(data2[:,7], data2[:,8]))
and it gave this error
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: operands could not be broadcast together with shapes (59427) (7,9)

What is the problem? and how to do that?

unutbu · Accepted Answer · 2013-10-26 10:39:46Z

1

data2[:7] should be data2[:,7] -- you missed a comma. data2[:7] apparently has shape (7,9), while data2[:,6] has shape (50427,). The error message is saying that the two arrays can not be broadcasted to a common shape upon which np.subtract can be applied.

x = data2[:,6] - data2[:,7]
y = data2[:,7] - data2[:,8]
pl.plot(x, y)

answered Oct 26, 2013 at 10:39

unutbu

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tacaswell Over a year ago

@user2154410 If this solved your problem please accept it (big gray check box on the left)

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