MATLAB: Extract the first negative value in a matrix column

findmatrixnegative values

I have a 501×100000 Matrix, containing positive and some negative values. The values were calculated using random numbers. I need the value, not the index of the first negative entry in each column. If there is no negative value in the column it should be displayed by a 0.

simplified example:

A = [ 1, 2, 5, 6; -1, 4, 8,-4; -2, 3, 9, 1; -2,-1, 3,-1 ]

The answer I need (for that example) is:

-1,-1,0,-4

Thanks in advance for any help…

Best Answer

Edit

out=arrayfun(@(x) min([ 0 A(find(A(:,x)<0,1),x)]),1:size(A,2))

Related Solutions

MATLAB: Keeping elements with specific conditions in a matrix

s = size(A);
B = A(rem(s(1) - sum(A ~= 999),s(1))+1 + s(1)*(0:s(2)-1));

ADD

t = A ~= 999;
tt = any(t);
out = 999*~tt;
[ii,jj] = find(t);
[b,b] = unique(jj,'first');
out(tt) = A(ii(b) + size(A,1)*(jj(b)-1));

out = repmat(999,1,size(A,2));
[ii,jj] = find(A ~= 999);
i1 = accumarray(jj,ii,[],@min);
idx = i1 + (0:max(jj)-1)'*size(A,1);
out(i1>0) = A( idx(i1>0));

t  = A ~= 999;
[jj,jj] = find(t);
out = accumarray(jj(:),A(t(:)),[],@(x)x(1)); % corrected
out = out + 999*~out

MATLAB: Find max and min of groups in columns of a matrix

a=[0 1;-3 3;-2 -7;0 5;4 -6;1 -2]
t = [true(1,size(a,2));diff(a<0)~=0];
ir = cumsum(t);
jj = max(ir);
ii = bsxfun(@plus,ir,[0,jj(1:end-1)]);
out1 = mat2cell(accumarray(ii(:),a(:),[],@(x)max(abs(x))*sign(sum(x))),jj,1);
out = cellfun(@(x)x(x~=0),out1,'un',0);

Best Answer

Related Solutions

MATLAB: Keeping elements with specific conditions in a matrix

MATLAB: Find max and min of groups in columns of a matrix

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