error: Undefined function 'log' for input arguments of type 'char' ((i can't determine the error source))

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mohammed 2014-12-19

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评论： mohammed 2014-12-24

采纳的回答： John D'Errico

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Stephen23 2014-12-19

The error message states that you are using the function log with a string input, for which it is not defined, as it only operates on floating point numbers. Given that you only use the log function twice, it should be fairly easy to locate which one has a string as its input.

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Answer 1

John D'Errico 2014-12-19

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编辑：John D'Errico 2014-12-19

在 MATLAB Online 中打开

Surely you can determine the source.

You have defined s as a string. Yes, that string looks like a number. But still, it is a string. See the difference in these two calls:

log(12)
ans =
       2.4849
log('12')
Undefined function 'log' for input arguments of type 'char'.

The log function is not defined to operate on strings, but you did that when you tried to execute the sub-expression log(s). Use log(k1) there instead. Or if you wanted to compute the log of your truncated approximation in the string s, then you will need to convert that number back into a number.

So you might need to use log(str2num(s)) instead of log(s).