Output arguments in functions

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Harry
Harry on 25 Jun 2013
In my code I have a some functions with an output argument c which seems to have caused some trouble as the errors are:
Error in image_processing_project>checkhorizontal (line 74)
for n = 0:steps
Output argument "c" (and maybe others) not assigned during call to
"C:\Users\bostock_h\Documents\MATLAB\image_processing_project.m>image_processing_project/checkhorizontal".
Error in image_processing_project/checkright (line 64)
c = checkhorizontal(i1,j,x1);
Error in image_processing_project (line 22)
c = checkright (i1,j);
and here is the code:
function image_processing_project
M = imread('C:\Users\bostock_h\Documents\Images\130510_162.jpg');
M = int16(M);
x = 975; %dimensions of the image
y = 1010;
sum=0;
global steps %the number of steps taken for the average
steps = 12;
global lowlimit %minimum value to pass
lowlimit = 40;
global highlimit %maximum value to pass
highlimit = 200;
global movel %amount of pixels moved to the left after check
movel = 10;
prog = 0;
pixelnum = (x - movel - 1)*y; %Total number of pixels in the image
%Main loop begin
for j = 1:y
for i1 = movel + 1:x
c = checkright (i1,j);
if c ~= 0
b = 1;
else
b = -1;
end
if c == 0
c = checkleft (i1,j);
end
if c == -1
if b == 1
M(j,i1-movel) = 1;
end
end
if c == 1
if b == 1
M(j,i1-movel) = 250;
end
end
if c == 1
if b == -1
M(j,i1+movel) = 250;
end
end
if c == -1
if b == -1
M(j,i1+movel) = 1;
end
end
prog = prog + 1;
percent = (prog / pixelnum) * 100
end
end
imagesc(M)
colormap(gray)
function c = checkright(i1,j)
x1 = 1;
c = checkhorizontal(i1,j,x1);
end
function c = checkleft(i1,j)
x1 = -1;
c = checkhorizontal(i1,j,x1);
end
function c = checkhorizontal(i1,j,x1)
for n = 0:steps
sum = M(j, i1 + n*x1) + sum;
end
avg = sum / steps;
if avg < lowlimit
c = -1*x1;
end
if avg > highlimit
c = 1*x1;
end
end
end

Answers (1)

Tom
Tom on 25 Jun 2013
In the CHECKHORIZONTAL function:
if avg < lowlimit
c = -1*x1;
end
if avg > highlimit
c = 1*x1;
end
means that if avg is neither below the low limit nor above the high limt, it won't be created in the function. Try setting adding an else statement which specifies a value of c and see if that helps.
  1 Comment
Harry
Harry on 25 Jun 2013
Thanks for the reply. I've changed that segment of code to:
if avg < lowlimit
c = -1*x1;
else c = 0;
end
if avg > highlimit
c = 1*x1;
else c = 0;
end
But that doesn't seem to have helped the errors regarding the c but has replaced the first error with a different one:
Subscript indices must either be real positive integers or logicals.
Error in image_processing_project/checkhorizontal (line 75)
sum = M(j, i1 + n*x1) + sum;
Error in image_processing_project/checkleft (line 70)
c = checkhorizontal(i1,j,x1);
Error in image_processing_project (line 31)
c = checkleft (i1,j);

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