Question

This is an easy question but say I have an MxN matrix. All I want to do is extract specific columns and store them in another numpy array but I get invalid syntax errors.
Here is the code:

extractedData = data[[:,1],[:,9]]. 

It seems like the above line should suffice but I guess not. I looked around but couldn’t find anything syntax wise regarding this specific scenario.

Answer 1

I assume you wanted columns 1 and 9?

To select multiple columns at once, use

X = data[:, [1, 9]]

To select one at a time, use

x, y = data[:, 1], data[:, 9]

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With names:

data[:, ['Column Name1','Column Name2']]

You can get the names from data.dtype.names…