pre allocating variables in matlab

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emeka onwochei
emeka onwochei 2021-3-3
评论： emeka onwochei 2021-3-4
i have this block of code but when i access elements, they are not arranged properly
x=zeros(1,10000);
y=zeros(1,10000);
count=1;
for i=1:rows
for j=1:columns
if imgThresh(i,j)==0
y(count)=rows-i+1;
x(count)=j;
count=count+1;
break
end
end
end
nonzeros(x)
nonzeros(y)
  2 个评论
James Tursa
James Tursa 2021-3-3
You need to give us a small example of input and desired output. Please describe specifically what it is about the output of your current code that you don't like. What are you trying to do?
emeka onwochei
emeka onwochei 2021-3-3
it supposed to read the binary image pixels and stores the cell of the first black box, it uses the points to draw a shape. it gives me the blue curve below.

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回答（1 个）

Walter Roberson
Walter Roberson 2021-3-4
Ran in:
That's not what I get.
imgThresh = im2bw(imread('image.png'));
rows = size(imgThresh,1);
columns = size(imgThresh,2);
x=zeros(1,10000);
y=zeros(1,10000);
count=1;
for i=1:rows
for j=1:columns
if imgThresh(i,j)==0
y(count)=rows-i+1;
x(count)=j;
count=count+1;
break
end
end
end
plot(x,y)
  1 个评论
emeka onwochei
emeka onwochei 2021-3-4
this is for the second part,
for i=1:rows
for j=fliplr(1:columns)
if imgThresh(i,j)==0
y(count)=rows-i+1;
x(count)=j;
count=count+1;
break
end
end
end

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