MATLAB: Average IF NaN counting

Question

Hi,

I have a 20*207 matrix which contains numbers and NaN.

I need to average each column if the amount of NaN is <5. If the number of NaN is >=5 then I would like to remove that column from the matrix. How can I do it? I've been trying some stuff but I'm not able to achieve it.

thanks.

Answer 1

Some test data

x = randn(20, 207);
x(randi(numel(x), 800, 1)) = nan;

Identify the NaNs with isnan and count the number per column with sum. Then select the columns that have fewer than 5 NaNs.

good_enough = sum(isnan(x)) < 5;
x = x(:, good_enough);

And use nanmean to take the average of the remaining columns.

avg = nanmean(x);

If you don't have the stats toolbox, try the following

the_nans = isnan(x);
num_nans = sum(isnan(x));
good_enough = num_nans < 5;
x = x(:, good_enough);
the_nans = the_nans(:, good_enough);
num_nans = num_nans(:, good_enough);
x(the_nans) = 0;
avg = sum(x);
avg = avg ./ (20 - num_nans);