How do I use for loops and if statements to find numbers in a two dimensional array and replace them?
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BCLAcowgirl#1
am 18 Feb. 2018
Kommentiert: Image Analyst
am 3 Okt. 2021
I need to replace all the negative numbers in A=[1 2 4; 3 2 -1; 2 4 5; -2 -1 10] with zeros using for loops and if statements.
Below is the coding I have, but it doesn't do anything. Please, advise me on what I'm doing wrong.
for i=A
if i<0
A(i)=0;
end
end
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Star Strider
am 18 Feb. 2018
In your homework assignment that requires for loops and an if block, you need two nested loops, one looping through the rows and another the columns. In the innermost loop, use the if statement to test and replace the negative values of ‘A’, not the loop indices (that in MATLAB must be integers greater than zero, so a test for negative values of them will always fail).
There are more straightforward ways to do this, one being:
A = [1 2 4; 3 2 -1; 2 4 5; -2 -1 10];
A = A .* (A>0)
A =
1 2 4
3 2 0
2 4 5
0 0 10
I don’t mind showing you that solution, since you can’t use it in your assignment.
2 Kommentare
Star Strider
am 18 Feb. 2018
You need to test for the value of ‘A(i,j)’ not the subscripts of ‘A(i,j)’.
I provided my solution as a hint as to how best for you to approach it.
Weitere Antworten (3)
Roger Stafford
am 18 Feb. 2018
Bearbeitet: Roger Stafford
am 18 Feb. 2018
Use the "linear" form of the array:
for i = 1:length(A(:))
if A(i) < 0 % <- [Corrected]
A(i) = 0;
end
end
or you can do this:
t = A<0;
A(t(:)) = 0;
1 Kommentar
Image Analyst
am 18 Feb. 2018
Close, but you need to loop from 1 to numel(A) and you need to check if A(i) < 0, not if i < 0.
A=[1 2 4; 3 2 -1; 2 4 5; -2 -1 10]
for i = 1 : numel(A)
if A(i) < 0
A(i) = 0;
end
end
A
0 Kommentare
Patel Keyur
am 3 Okt. 2021
I have one array and in this array detected number in this array so how to detected number in array?
1 Kommentar
Image Analyst
am 3 Okt. 2021
Use == (if they're integers) or ismembertol() if they're floating point numbers.
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