Using sscanf (or equivalent) to extract double from string.

Question

James 2014-11-26

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/164424-using-sscanf-or-equivalent-to-extract-double-from-string

回答： Stephen23 2014-12-1

采纳的回答： Stephen23

在 MATLAB Online 中打开

Let's say I have a string as follows:

string = '2.3A 4B C'

I want to apply a function that will output the following:

[2.3 4 1]

where these values are simply the "prefixes" (converted to doubles) of the letters specified within the string. One important note is that any letter lacking a prefix should output a 1.

My first thought was to use sscanf and include some condition for letters lacking prefixes, but it hasn't quite worked the way I'd like.

Any suggestions from the Matlab world?

Thanks!

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Stephen23 2014-12-1

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/164424-using-sscanf-or-equivalent-to-extract-double-from-string#answer_160796

在 MATLAB Online 中打开

This solution uses regexp to detect the sequences of characters (possibly with leading digits and optional decimal fraction). It returns the numeric parts, which are then converted to floating point numbers. Any empty cells are given the value 1, then the whole thing is converted to a numeric array.

>> str = '2.3A 4B C';
>> A = regexp(str,'(\d+(\.\d+)?)?[A-Z]+','tokens');
>> A = [A{:}];
>> A = cellfun(@str2num,A,'UniformOutput',false);
>> A{cellfun('isempty',A)} = 1;
>> A = [A{:}]
A =
          2.3            4            1

No loops, no cluttering up of the workspace... elegance is never overrated!

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

Answer 2

James 2014-11-26

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/164424-using-sscanf-or-equivalent-to-extract-double-from-string#answer_160355

在 MATLAB Online 中打开

Well, this seems to work. Elegance is overrated, right? aha

 name = '2.3A 4B C';
 letterIndex = regexp(name,'[A-Z]');
 letterNum = 1;
 floatLength = 0;
 outVal = zeros(1,length(letterIndex));
 for i = 1:length(name)
   if i == letterIndex(letterNum)
       if floatLength == 1
          outVal(letterNum) = 1;
       else
           outVal(letterNum) = str2double(name((i-floatLength):(i-1)));
       end
       floatLength = 0;
       letterNum = letterNum + 1;
   else
       floatLength = floatLength + 1;
   end
 end