How to pass input parameter in a function handle

Question

etudiant_is 2016-6-13

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/289528-how-to-pass-input-parameter-in-a-function-handle

评论： etudiant_is 2016-6-14

I don't know what it is really called so maybe the title of my question can be misleading. Anyway, I am using simulated annealing and I initially set the options as follows

options = saoptimset('DataType', 'custom', 'AnnealingFcn', @PermuteElements, ...
       'StallIterLimit',50, 'ReannealInterval',50, 'PlotInterval', 50, 'AcceptanceFcn', @acceptancesa);

then I called simulated annealing with these options and it works fine.

The problem is that I want to have some input parameters for the function PermuteElements(param1,param2,etc) which I will need inside the function. but when I add them in the options

options = saoptimset(..., @PermuteElements(param1,param2,etc), ...);

I get an error. I don't exactly understand the role of the @ in front of the function. So how should I input the parameters to the function? Also, how can I figure out when (and by which function) will the function I made exactly be called during simulated annealing execution?

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

Guillaume 2016-6-13

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/289528-how-to-pass-input-parameter-in-a-function-handle#answer_225300

编辑：Guillaume 2016-6-13

在 MATLAB Online 中打开

Yes, you simply need to wrap your function handle into an anonymous function where the parameters are set. In your case:

%%in your function where param1 is defined and saoptimset is called
param1 = ... %must be set before the anonymous function is created
PermEl = @(optimValues) PermuteElements(param1, optimValues);
%note that changes to param1 from then on will not affect PermEl. param1 value has in effect become a constant in PermEl
options = saoptimset('DataType', 'custom', 'AnnealingFcn', PermEl, ...
     'StallIterLimit',50, 'ReannealInterval',50, 'PlotInterval', 50, 'AcceptanceFcn', @acceptancesa);

In effect, the anonymous function is equivalent to creating a function that does

function NewPoint = PermEl(optimValues)
   NewPoint = PermuteElements(param1, optimValues) %with param1 defined by the main code
end

except that the above does not work because standard functions have no way of accessing the variables from another function, so param1 would be undefined. Anonymous functions and nested functions can do the capture.

7 个评论
显示 5更早的评论隐藏 5更早的评论

Guillaume 2016-6-13

编辑：Guillaume 2016-6-13

在 MATLAB Online 中打开

Well, there you go, the optimiser passes two arguments to the function handle so the anonymous function must accept two arguments.

You can either ignore that extra argument in the anonymous function:

PermEl = @(optimValues, ~) PermuteElements(param1, optimValues);

with PermuteElements defined as:

function NewPoint = PermuteElements(param1, optimValues)

or ignore it in PermuteElements:

PermEl = @(optimValues, problemData) PermuteElements(param1, optimValues, problemData)

with PermuteElements defined as:

function NewPoint = PermuteElements(param1, optimValues, ~)

etudiant_is 2016-6-14

Thanks, now it works fine :).

请先登录，再进行评论。

Answer 2

the cyclist 2016-6-13

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/289528-how-to-pass-input-parameter-in-a-function-handle#answer_225281

I think what you are trying to do is described in this documentation page.

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

etudiant_is 2016-6-13

编辑：etudiant_is 2016-6-13

在 MATLAB Online 中打开

I tried to do it with anonymous function but it is still not right. In fact, PermuteElements takes as an input parameter optimValues which is produced during the simulated annealing process and I want to have another input with it from when I first call the simulated annealing. (the two parameters are not available at the same function/workspace) Basically the header of my function is like this

function NewPoint = PermuteElements(param1, optimValues)

I can not do

PermEl=@(x) PermuteElements(param1,optimValues)

then

options = saoptimset(..., PermEl, ...);

because optimValues does not exist at that step yet.

请先登录，再进行评论。