Performing math.sqrt on numpy structured array column

Question

I have a numpy structured array. The final column needs to contain the result of a simple math equation based on the other values in the row. Problem is I get the following error when trying to calculate the square root portion of the equation:

TypeError: only length-1 arrays can be converted to Python scalars

Limitation is that I cannot iterate the array to add the values one at a time.

Here's an example to show the error:

import numpy as np import math data = np.random.randint(-100, 100, (1, 6, 4)) data[:,3] = math.sqrt((0-data[:,0])**2 + (0-data[:,1])**2 + (0-data[:,2])**2)

John Zwinck · Accepted Answer · 2014-09-25 05:27:05Z

6

You simply need to use np.sqrt instead of math.sqrt (the latter only works on single values).

answered Sep 25, 2014 at 5:27

John Zwinck

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1 Comment

Carl Over a year ago

Silly me! Thanks for picking that up.

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