Counting values above a threshold within a matrix.

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Gareth Evans
Gareth Evans 2012-9-17
评论： Emmagnio Desir 2023-9-5
Hello,
Im looking at finding a way of counting values that are >0 from a matrix, for example:-
if true %if statement used to display matrix correctly
00100
01110
11111
01110
00100
end
Would provide the output 1,3,5,3,1. Any help would light up my day.
Cheers
Gareth

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采纳的回答

Greg
Greg 2012-9-17
sum(myMat>0, 2)
the result is the number of values in each row > 0.
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Gareth Evans
Gareth Evans 2012-9-17
A little closer to the solution, for which i really appreciate.
Say the matrix is a 24X365 where 24 is equal to hours and 365 to days. This matrix contains values which relate to the intensity of sunlight hourly per day for 365 days.
How can i create an output from the matrix that will provide a matrix (1X365) with each cell in the matrix (1x365) containing values that exceed 0. or in other words how many hours a day sunlight per day?
I hope this makes the problem clearer as the code given above is outputting the wrong dimensions. and i cant seem to get the right solution by playing with it.
cheers guys.

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更多回答（2 个）

Babak
Babak 2012-9-17
you can run the below function for each of your numbers:
function num_of_1s = no1(n)
if n==0
num_of_1s = 0;
else
length = floor(log10(n))+1;
num_of_1s = 0;
for j=length:-1:1
if floor(log10(n)) == j-1
num_of_1s = num_of_1s +1;
n = n-10^(j-1);
end
end
end
end
Then say for example:
no1(1010111)
which returns
5
  1 个评论
Gareth Evans
Gareth Evans 2012-9-17
I do apologise, I believe that the way i used to display the matrix using this forum editor might of caused a little confusion. I used the code tab to enable me to display the matrix as you would write down on a piece of paper.
00200 03450 12345 06540 00300 would be a 5x5 matrix.
Could you solve this problem with out an if loop?
with thanks.

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nah
nah 2012-9-17
A simple way is:
myMat =
0 0 2 0 0
0 3 4 5 0
1 2 3 4 5
0 6 5 4 0
0 0 3 0 0
[nrows,ncols] = size(myMat);
counts_above_0 = zeros(nrows,1);
for rx = 1:nrows
counts_above_0(rx,1) = length(find(myMat(rx,:)>0));
end

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