How to skip error and continue (NOT in loop)?

Question

n33 2019-4-5

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https://ww2.mathworks.cn/matlabcentral/answers/454555-how-to-skip-error-and-continue-not-in-loop

评论： Walter Roberson 2023-5-11

If I have the following code, how to display x(10) after x(9999) causing an error?

x = ones(1, 10);
try
    x(1)
    x(9999)
    x(10)
catch ME
    fprintf(ME.message)
end

The output I got is:

ans =
     1
Index exceeds the number of array elements (10).

Thanks!

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Answer 1

Walter Roberson 2019-4-5

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https://ww2.mathworks.cn/matlabcentral/answers/454555-how-to-skip-error-and-continue-not-in-loop#answer_369160

在 MATLAB Online 中打开

x = ones(1,10);
idx = [1 9999 10];
for K = 1 : length(idx)
    try
        x(K)
    catch ME
      fprintf(ME.message)
    end
end

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Fernando 2023-5-11

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if one has commands that truly cannot be done in a loop, then how can you skip a command error without having to try/catch every single command?

say:

A = command1thatcanpossiblycauseanerror;
B = command2thatcanpossiblycauseanerror;
C = command3thatcanpossiblycauseanerror;
D = command4thatcanpossiblycauseanerror;
E = command5thatcanpossiblycauseanerror;
F = command6thatcanpossiblycauseanerror;
G = command7thatcanpossiblycauseanerror;
H = command8thatcanpossiblycauseanerror;
I = command9thatcanpossiblycauseanerror;
J = command10thatcanpossiblycauseanerror;
K = command11thatcanpossiblycauseanerror;
L = command12thatcanpossiblycauseanerror;
M = command13thatcanpossiblycauseanerror;
N = command14thatcanpossiblycauseanerror;
O = command15thatcanpossiblycauseanerror;
P = command16thatcanpossiblycauseanerror;
Q = command17thatcanpossiblycauseanerror;
R = command18thatcanpossiblycauseanerror;
S = command19thatcanpossiblycauseanerror;
T = command20thatcanpossiblycauseanerror;
U = command21thatcanpossiblycauseanerror;
V = command22thatcanpossiblycauseanerror;
W = command23thatcanpossiblycauseanerror;
X = command24thatcanpossiblycauseanerror;
Y = command25thatcanpossiblycauseanerror;
Z = command26thatcanpossiblycauseanerror;
%where each commandXXthatcanpossiblycauseanerror is some command, really
%anything, something that cannot possibly be in a for loop.
%as the author asked.

Steven Lord 2023-5-11

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A = command1thatcanpossiblycauseanerror;
B = command2thatcanpossiblycauseanerror;
C = command3thatcanpossiblycauseanerror;
D = command4thatcanpossiblycauseanerror;
% etc

That has a similar code smell to the frequently asked question about dynamically creating variables with numbered names like x1, x2, x3, etc., for which the general consensus is to avoid doing that.

Rather than posing a hypothetical scenario, can you share a little more detail about your actual application where you use a pattern like that code? What do those commands that can possibly throw an error do? Are they independent or are the outputs of one or more of those functions the inputs to later of those functions?

Walter Roberson 2023-5-11

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I am having difficulty thinking of any code that is such that

A = command1thatcanpossiblycauseanerror;

is valid code, but

for dfpSzcGKKqyMbgIcvYXqkicEiRRKtIUpb_vjDshBQupYrSfhm_GS_xNidaex = 1 : 1
    A = command1thatcanpossiblycauseanerror;
end

"cannot" work.

The only things I can come up with are along the lines of "needing" dbstack to be able to pinpoint the function name... ummm, no, even that would not explain things.

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