How to save a data when something happens

2013 11 17
3 个回答
更新时间：2013 11 18
3 次查看（30 天）

0 个投票

Hello everybody, I am receiving 100 symbols, with values starting from 0 and go to 1. The scenario is like this.
for i=1:100
if Symbolvalue >= 0.5
Nuberofsymbolvalue=i;
end;
end;
I need to save the the first i in which I go above 0.5
Thanks in advance.

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回答（3 个）

Image Analyst
Image Analyst 2013-11-17
编辑：Image Analyst 2013-11-17

0 个投票

if symbolValue > 0.51
savedSymbolValue = symbolValue;
% Optionally save to a mat file
save(yourMatFileName, 'savedSymbolValue');
end

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mahdi safarzadeh
mahdi safarzadeh 2013-11-17
thanx a lot. But i dont want to save symbol value, I want to save the number in which symbol value goes above 0.5 if I use a if like this:
if symbolvalues >= 0.5
Numberofsymbol=n;
end;
this way, I am not able to save the first time I go above my threshold!
I want to save the number of that symbol in which the first time go above the threshold.
mahdi safarzadeh
mahdi safarzadeh 2013-11-17
The scenario is like this, But I need to save the the first i in which I go above 0.5
for i=1:100
if Symbolvalue >= 0.5
Nuberofsymbolvalue=i;
end;
end;
Image Analyst
Image Analyst 2013-11-17
OK, you didn't have any explanation at first so I just went with what I could. Now that I see what you're after I recommend:
Nuberofsymbolvalue = find(Symbolvalue > 0.5, 1, 'first'); % Save the index
No loop over i is needed. If you wanted to find out the value at that index, do this:
theSymbolValue = Symbolvalue(Nuberofsymbolvalue);
though you might want to use Number instead of Nuber (unless Nuber means Number in your language)
mahdi safarzadeh
mahdi safarzadeh 2013-11-18
Thanks a lot for your answer. the find() function solution is way simpler and i am gonna try to use it in my codes. Thanks a agin.
Image Analyst
Image Analyst 2013-11-18
Please mark the best answer as "Accepted" if you're done with this topic. Thanks.

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Umair Nadeem
Umair Nadeem 2013-11-17
编辑：Umair Nadeem 2013-11-17

0 个投票

you can use this
index = 1;
for i = 1:100
if SymbolValue >= 0.5
NumberofSymbolValue[index] = i;
index += 1;
end
end
Valueoffirst_i = NumberofSymbolValue[1];
The first value in array NumberofSymbolValue will show the first i
Hope it helps

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Walter Roberson
Walter Roberson 2013-11-17
MATLAB does not use { and } for grouping: it uses "end" to mark the end of a block.
mahdi safarzadeh
mahdi safarzadeh 2013-11-17
Thanks a lot Umair, your solution worked :))))
Image Analyst
Image Analyst 2013-11-17
编辑：Image Analyst 2013-11-17
How did it work? Are you programming in C? MATLAB doesn't use [] around array indexes and doesn't have the += operator. Plus, his solution could be done with a non-looping simple call to find like Walter and my solution.
allHighSymbolIndexes = find(Symbolvalue >= 0.5)
mahdi safarzadeh
mahdi safarzadeh 2013-11-18
of course I changed the C to Matlab code. the "find()" function solution is way simpler, I am gonna try to use it in my codes. But Umair's solution worked for may case. Thanks anyway.

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Walter Roberson
Walter Roberson 2013-11-17

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find(Symbolvalue >= 0.5, 1, 'first')

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mahdi safarzadeh
mahdi safarzadeh 2013-11-17
Thanks a lot Walter, your solution looks really tempting but I dont know why it didnt work for my case! anyway, thanks a lot.
Image Analyst
Image Analyst 2013-11-17
Just assign the output to something:
firstHighSymbolIndex = find(Symbolvalue >= 0.5, 1, 'first')
theFirstHighSymbol = Symbolvalue(firstHighSymbolIndex);
We don't know why it didn't work because you didn't show your code. The code you used (a for loop) is not vectorized and not as MATLAB-ish but is probably still fast enough.

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