Matlab：如果矩陣中包含多個特定數量的NaN值，如何刪除矩陣中的所有列

Question

我想刪除所有具有超過一定數量NaN的列（比如5個NaN）。 有沒有辦法沒有循環呢？

Answer 1

無需循環：

matFixed = MAT( :, sum( isnan( MAT ) ) <= 5);

一步步：

nanMat = isnan(MAT); % convert MAT to logical with 1 indicating value is a NAN
nNanInCol = sum(nanMat); %compute the number of NANs in each col
colIdx = nNanInCol <= 5; % determine which columns are "valid"
matFixed = MAT(:, colIdx); % create new matrix using only the good columns of MAT

Answer 2

這很容易：

%# define a matrix with NaNs
A = rand(10); %# 10x10 array
A(A<0.5) = NaN; %# each column contains on average 5 NaNs

%# count NaNs
nanCt = sum(isnan(A),1);

%# remove columns with too many NaNs
A(:,nanCt > 5) = [];