Is this program free from bugs? The program is to find the position of the element greater than 100.

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Khiyanat Deori 2020-7-11

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评论： Walter Roberson 2020-7-12

%% Example
for ii= 1:length(readings)
  if readings(ii)>100
    fprintf('first reading above 100 is at position %d\n', ii);
   return;
  
  end
end
  fprintf('no values greater than 100 upto position %d\n',ii);

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Answer 1

Walter Roberson 2020-7-11

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The program will not work properly if readings is two or more dimensional.

The program will fail when it encounters the return statement: return is only permitted in functions.

The program will fail if readings is something that is not comparable to a number, such as if it is a cell array or transfer function.

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Khiyanat Deori 2020-7-12

Thankfully the value assigned to readings was a double array.

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Answer 2

Image Analyst 2020-7-11

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If readings is a double array, you could do this:

index = find(readings > 100, 1, 'first');
if isempty(index)
    fprintf('No value greater than 100 was found.\n');
else
    fprintf('First value greater than 100 was found at index %d and has a value of %f.\n', index, readings(index));
end

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Image Analyst 2020-7-12

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It's normal for something to be printed, yes. That's what fprintf() does. If only the first fprintf() gets executed, then there are no values above 100. If the second one gets executed then there will be at least one value above 100. Here is a demo:

% First have no values more than 100
readings = [1,2,3,4]
index = find(readings > 100, 1, 'first');
if isempty(index)
    fprintf('No value greater than 100 was found.\n');
else
    fprintf('First value greater than 100 was found at index %d and has a value of %f.\n', index, readings(index));
end
% Now, have several values more than 100
readings = [1,2,3,400, 900, 7,6,5]
index = find(readings > 100, 1, 'first');
if isempty(index)
    fprintf('No value greater than 100 was found.\n');
else
    fprintf('First value greater than 100 was found at index %d and has a value of %f.\n', index, readings(index));
end

It prints the two cases to the command window:

readings =

1 2 3 4

No value greater than 100 was found.

readings =

1 2 3 400 900 7 6 5

First value greater than 100 was found at index 4 and has a value of 400.000000.

I guess I just don't see why this is confusing to you. Do you expect the second fprintf() to print even when there are no values above 100? If so, why? Please attach your readings and tell me what you think it should print.