replace nan with a value

I have a column in which some values are missing and shown as NaN. I need to replace all these NaN with the median of the column. Here is what I tried: I am extracting column 4 in which there are missing values, find the median value, Use isnan to replace the logical 1 with the median.

Column 4 values: 1 2 3 4 5 6 NaN 12 10 NaN 4 5 NaN

     C=num(:,4);
     median=nanmedian(C);
     R(isnan(C))=median;

But with this I am getting results as : 0 0 0 0 0 0 12 0 0 12 0 0 12

But the expected result is: 1 2 3 4 5 6 12 12 10 12 4 5 12

Any suggestions ?

Answer 1

[Star Strider]

Please do not use ‘median’ as a variable name.

I don’t know where the ‘12’ value comes from, since the median of the vector you posted is 4.5.

Other than that, ‘R’ does not magickally become ‘C’. You have to create it first.

This works for me:

C = [1 2 3 4 5 6 NaN 12 10 NaN 4 5 NaN]';
median_4 = nanmedian(C);
R = C;
R(isnan(C)) = median_4;

[Daphne Mariaravi]

The median value 12 wasn't actually calculated. I just filled in some random values just to give a picture of what my problem was. Sorry about that. The code works! Thanks

[Star Strider]

My pleasure!

Answer 2

[Steven Lord]

If you're using release R2016b or later use fillmissing.

z = [1 2 3 4 5 6 NaN 12 10 NaN 4 5 NaN].';
y = fillmissing(z, 'constant', median(z, 'omitnan'));
showBothColumnsSideBySide = [z, y]

[Daphne Mariaravi]

@stevenLord using the fillmissing I am getting the following error "Subscript indices must either be real positive integers or logicals."

[Jan]

@Daphne: This happens, because "median" was defined as a variable on your computer. Do not shadow builtin functions by variables. Solution: Restart Matlab or:

clear median

[Daphne Mariaravi]

Yes. Got it! Thank you