How do I write an if loop in a nested for loop
显示 更早的评论
I am trying to create a list of instances where x is equal to y, where x and y are created by a nested for loop. However, the if statement seems to only run through the first iteration of the loop.
radiusincrement = 1;
thetaincrement = 45;
k=1;
for i=1:1:5/radiusincrement %two for loops that will sweep through wafer points
for j=1:1:thetatotal
r(i,j) = (i-1)*radiusincrement;
theta(i,j) = (j-1)*thetaincrement;
x(i,j) = r(i,j).*cos(theta(i,j).*pi/180);
y(i,j) = r(i,j).*sin(theta(i,j).*pi/180);
point = [x(i,j) y(i,j) 0];
if point(1)==point(2)
kx(k)=x(i,j);
ky(k)=y(i,j);
k=k+1;
end
end
end
What am I doing wrong? Thanks!
采纳的回答
Welcome to the world of floats. Just as you can't write 1/3 in decimal with a finite number of digits, computers can't store exact values sometimes. Run the code below and you will have your answer.
radiusincrement = 1;
thetaincrement = 45;
thetatotal=3;
k=1;
for i=1:1:5/radiusincrement %two for loops that will sweep through wafer points
for j=1:1:thetatotal
r(i,j) = (i-1)*radiusincrement;
theta(i,j) = (j-1)*thetaincrement;
x(i,j) = r(i,j).*cos(theta(i,j).*pi/180);
y(i,j) = r(i,j).*sin(theta(i,j).*pi/180);
point = [x(i,j) y(i,j) 0];
if point(1)==point(2)
kx(k)=x(i,j);
ky(k)=y(i,j);
k=k+1;
elseif abs(point(1)-point(2))<=(1e-10)
disp('you should have compared against a tolerance')
end
end
end
Two side notes:
If x and y are equal, why bothering storing them separately?
Did you consider doing this with an array operation?
2 个评论
Walker Boldman
2020-5-13
Rik
2020-5-13
You're welcome. If I solved your question, please consider marking it as accepted answer, if not, feel free to comment with your remaining issues.
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