MATLAB: Sorting NaN

sort

say if i have a matrix a:

a=[1 2 3;4 5 6;7 8 9;NaN NaN NaN]

i want to sort this in descending order, so i use

sort(a,1,'descend')

but the problem is, matlab puts the NaN at the top, is there a way to make it so that NaN is at the bottom? Thanks

Best Answer

As long as you don't have any -Inf values in a, you could always do a quick hack:

a=[1 2 3;4 5 6;7 8 9;NaN NaN NaN]
a(isnan(a)) = -Inf;
a = sort(a,1,'descend');
a(isinf(a)) = NaN

Related Solutions

MATLAB: Correlation between two row matrices

Like that, each value of "a" is correlated to each value of "b", but applying the formula of the correlation, the correlation of two single numbers is NaN. To compute the correlation correctly, traspose the input vectors

result  = corr(a', b');

MATLAB: Replace a number in a matrix depending on neighbor numbers

It is unclear if elements connected diagonally count as neighbours. If not, then you could try something like this.

%%Work with At to keep A intact
At=A;
%%Replace NaN with some number
At(isnan(At))=9;
%%B is for saving index of new NaNs
B=zeros(size(At));
%%Find sequences of [2 NaN] and [NaN 2] row-wise
for i=1:size(At,1)
B(i,strfind(At(i,:),[9 2])+1)=NaN;
B(i,strfind(At(i,:),[2 9]))=NaN;
end
%%Transpose A and repeat (same as column-wise)
At=At';
for i=1:size(At,2)
B(strfind(At(i,:),[9 2])+1,i)=NaN;
B(strfind(At(i,:),[2 9]),i)=NaN;
end
A(isnan(B))=NaN

ans =

   NaN   NaN   NaN   NaN   NaN   NaN   NaN
   NaN   NaN   NaN   NaN   NaN   NaN   NaN
   NaN   NaN     1     1     1   NaN   NaN
   NaN   NaN     1     2     1   NaN   NaN
   NaN   NaN     1     1     1   NaN   NaN
   NaN   NaN   NaN   NaN   NaN   NaN   NaN
   NaN   NaN   NaN   NaN   NaN   NaN   NaN

Best Answer

Related Solutions

MATLAB: Correlation between two row matrices

MATLAB: Replace a number in a matrix depending on neighbor numbers

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