Calling functions inside another function

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Simona Ondrckova
Simona Ondrckova 2017-11-13
评论： Simona Ondrckova 2017-11-13
Hello, I have a problem with calling a function inside another function. I have a function PLearn that looks like this:
function LPar = PLearn(input,desOut,Par)
p = perc_learn(Par{1},input,desOut,Par{2},Par{3});
LPar = {p};
end
Then I have a function Err which gets in a parameter Name name of the function it should call (PLearn). This is the code for Err:
function E=Err(Name,NameL,Param,Tr,DTr,Ts,DTs)
%Lpar=PLearn(Tr,Dtr,Param);
Lpar=@Name(Tr,Dtr,Param);
dif=0;
for i = 1:size(Ts,2)
input=Ts(:,i);
%Out=@NameL(LPar,input);
Out=PRecall(Lpar,input);
dif=dif+abs(DTs(i)-Out);
end
% To make sure that err is a value between 0 and 1
% I will divide the number of miscalculated vectors by the total number of input vectors.
E=double(dif/size(Ts,2));
end
I call Err with these parameters:
Err(PLearn,PRecall,p,In,InO,TIn,TInO).
Now Err calls PLearn by passing pararametrs p,In and InO into it. It gives me this error:
In D:/FreematWorkspace/k-fold/PLearn.m(PLearn) at line 2
Error: Undefined function or variable Par
But if I run PLearn straight (by typing PLearn(In,InO,P)) with the same parameters it calculates the result no problem. So I don't get why it doesn't work through Err. I thought the problem might be with the use of name and calling the function through @ but even if I just call PLearn straight up from Err (the commented version) it still gives me the same error. I would appreciate any help on how to fix this.
Thank you so much

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回答（1 个）

Steven Lord
Steven Lord 2017-11-13
Lpar=@Name(Tr,Dtr,Param);
That's not the right way to define an anonymous function.
Err(PLearn,PRecall,p,In,InO,TIn,TInO).
This will try to call PLearn with 0 input arguments and pass the output from that call into Err. [Actually, it probably should throw an error about the trailing period first.]
If you want to "pass one function into another", don't pass the name of the first function into the second. Instead pass a function handle to the first function into the second. [That function handle could be an anonymous function.]
Your call would become:
Err(@PLearn, @PRecall, p, In, InO, TIn, TInO)
To evaluate that function handle inside Err:
function E=Err(fun,funL,Param,Tr,DTr,Ts,DTs)
value = fun(Tr, DTr, Param);
% etc
Search the documentation for the terms "anonymous function" and "function handle" for more information.
  1 个评论
Simona Ondrckova
Simona Ondrckova 2017-11-13
Ohh I see now. Thank you. I have adjusted that but it still finds an error, this time it says:
Error: Unsupported type for call to toArrayVector
at line 2 in PLearn.
And again if I just run it straight through PLearn it has no problems. My Err function now looks like this:
function E=Err(Name,NameL,Param,Tr,Dtr,Ts,DTs)
Lpar=Name(Tr,Dtr,Param);
dif=0;
for i = 1:size(Ts,2)
input=Ts(:,i);
Out=NameL(Lpar,input);
dif=dif+abs(DTs(i)-Out);
end
% To make sure that err is a value between 0 and 1
% I will divide the number of miscalculated
% vectors by the total number of input vectors.
E=double(dif/size(Ts,2));
end
and I call it with:
Err(@PLearn,@PRecall,p,In,InO,TIn,TInO)

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