Removing nan values from an array

python arrays numpy nan
Dax Feliz picture Dax Feliz · Jul 23, 2012 · Viewed 416.6k times · Source

I want to figure out how to remove nan values from my array. My array looks something like this: 

x = [1400, 1500, 1600, nan, nan, nan ,1700] #Not in this exact configuration

How can I remove the nan values from x?

Answer

jmetz picture jmetz · Jul 23, 2012

If you're using numpy for your arrays, you can also use

x = x[numpy.logical_not(numpy.isnan(x))]

Equivalently 

x = x[~numpy.isnan(x)]

[Thanks to chbrown for the added shorthand]

Explanation

The inner function, numpy.isnan returns a boolean/logical array which has the value True everywhere that x is not-a-number. As we want the opposite, we use the logical-not operator, ~ to get an array with Trues everywhere that x is a valid number.

Lastly we use this logical array to index into the original array x, to retrieve just the non-NaN values.

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