str2num strange behaviour

1 次查看（过去 30 天）
Elena Casiraghi
Elena Casiraghi 2019-8-23
评论： Elena Casiraghi 2019-8-24
Dear, I have this code:
svmKernel ={'rbf','gaussian', 'linear','2','3','4'};
for k=1:numel(svmKernel)
[p, status] = str2num(svmKernel{k});
if ~status; t = templateSVM('Standardize',true,'KernelFunction',svmKernel{indK});
else; t = templateSVM('Standardize',true,'KernelFunction','polynomial', 'PolynomialOrder', p); end
WHY str2num returns p =
Linear Function:
Parameters: [1×1 struct]
and status = 1 when issuing [p,status] = str2num('linear')?
[p, status] = str2num('linear')
Linear Function:
Parameters: [1×1 struct]
status =
logical
1
  6 个评论
显示 4更早的评论
Elena Casiraghi
Elena Casiraghi 2019-8-23
Thanks!
This is a good information!
Elena Casiraghi
Elena Casiraghi 2019-8-23
By the way, This is my result
which str2num
C:\Program Files\MATLAB\R2018a\toolbox\matlab\strfun\str2num.m

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Stephen23
Stephen23 2019-8-23
编辑：Stephen23 2019-8-23
"str2num strange behaviour"
It is not strange behavior at all: str2num (unfortunately) relies on eval, as the str2num help clearly states "...str2num uses the eval function, which can cause unintended side effects when the input includes a function name." You provided str2num a function name to evaluate... you can easily find out which function it is evaluating:
which linear -all
As the str2num documentation recommends, you could avoid the whole problem simply by using str2double (which could be called before the loop), then using isnan.
  3 个评论
显示 1更早的评论
Steven Lord
Steven Lord 2019-8-23
Another solution would be to avoid trying to convert that text data into numbers entirely.
svmKernel = {{'rbf'}, ...
{'gaussian'}, ...
{'linear'}, ...
{'polynomial', 'PolynomialOrder', 2}, ...
{'polynomial', 'PolynomialOrder', 3}, ...
{'polynomial', 'PolynomialOrder', 4}};
for k=1:numel(svmKernel)
t = templateSVM('Standardize',true,'KernelFunction', svmKernel{k}{:});
end
The command svmKernel{k} extracts the contents of each cell inside svmKernel in turn. Since I have cell arrays inside each of those cells, I can turn them into a comma-separated list. This is the technique shown in the "Function Call Arguments" example in the "How to Use the Comma-Separated Lists" item on that documentation page.
Elena Casiraghi
Elena Casiraghi 2019-8-24
Tkanks Stephen!
I didin't know that! :)

请先登录，再进行评论。

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Cell Arrays 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by