Sum of each row ?

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Trevor Badji
Trevor Badji on 10 Dec 2017
Commented: Image Analyst on 26 Dec 2017
I have [1 1 0; 0 1 0; 0 0 0;] and I want to write that if average of each row > 0.5 it equals 1 , else 0
for the example above, first row 1+1+0 / 3 > 0.5 then it is 1 ..
for i=1:length(nx);
s(i)= sum(nx(i,:))/3;
for n=1:length(nx);
if s(i(n+1))> 0.5;
s(i(n+1)) == 1;
else
s(i(n+1))== 0 ;
end
end
end
  2 Comments
Star Strider
Star Strider on 10 Dec 2017
What functions are you permitted to use in this obvious homework assignment?
Rena Berman
Rena Berman on 26 Dec 2017
(Answers Dev) Restored edit

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Answers (3)

Jos (10584)
Jos (10584) on 10 Dec 2017
Use the matlab way! Use the functions mean, or sum and size. Read the documentation on these functions and pay attention to the dimension argument.
Then take a closer look at logical operators, like >
A = [.9 .7 .4 .6 .2]
B = A > 0.5

Image Analyst
Image Analyst on 10 Dec 2017
Edited: Image Analyst on 10 Dec 2017
Does it have to be a for loop? Why not just do:
rowMeans = mean(nx, 2);
s = zeros(size(nx));
s(rowMeans > 0.5, :) = 1;
You've said both "sum" and "average" - which is it?????. The above is for average. If you want sums, do
rowSums = sum(nx, 2);
s = zeros(size(nx));
s(rowSums > 0.5, :) = 1;
  3 Comments
Stephen23
Stephen23 on 11 Dec 2017
"There are no specific number of rows therefore i am trying to use for loop to see average of each row"
This makes no sense: vectorized code has no restrictions on how many rows it can handle. Why do you think that a loop is required?
Image Analyst
Image Analyst on 26 Dec 2017
Original question:
I have [1 1 0; 0 1 0; 0 0 0;] and I want to write that if average of each row > 0.5 it equals 1 , else 0
for the example above, first row 1+1+0 / 3 > 0.5 then it is 1 ..
for i=1:length(nx);
s(i)= sum(nx(i,:))/3;
for n=1:length(nx);
if s(i(n+1))> 0.5;
s(i(n+1)) == 1;
else
s(i(n+1))== 0 ;
end
end
end

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Walter Roberson
Walter Roberson on 10 Dec 2017
mean(nx, 2) > 0.5 %the 2 means "by rows" here.

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