strange error with varfun and anonymous function

Question

clauper 2022-12-21

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1882377-strange-error-with-varfun-and-anonymous-function

评论： Bjorn Gustavsson 2022-12-22

The following example:

tbl = table(randn(5,1));
func = @(x) cumsum(x);
varfun(@func, tbl)

gives me the error:

Error using tabular/varfun>dfltErrHandler (line 436)

Applying the function 'func' to the variable 'Var1' generated the following error:

Undefined function 'func' for input arguments of type 'double'.

Is this a bug in matlab, or am I doing something wrong?

P.S. varfun(@cumsum, tbl) works without error

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Answer 1

Bjorn Gustavsson 2022-12-21

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https://ww2.mathworks.cn/matlabcentral/answers/1882377-strange-error-with-varfun-and-anonymous-function#answer_1133117

在 MATLAB Online 中打开

These 2 modifications work:

tbl = table(randn(5,1));
func = @(x) cumsum(x);
varfun(func, tbl) 
% ans =
%  5x1 table
%    Fun_Var1
%    ________
%    0.53767 
%     2.3716 
%    0.11271 
%    0.97488 
%     1.2936 
varfun(@(x) func(x), tbl)

I've (that is a major warning-flag!) have come to see this as func being a function handle, not the function itself function. varfun expects a function-handle, and I've come to see your construct:

varfun(@func, tbl)

as

varfun(@ @cumsum, tbl)

Which would be handle-function-handle or some such wrong-order type.

HTH