COM: matlabObj.Feval() - works for calling one function, how would it work for calling a nested set of functions?

Question

Andy 2024-4-21

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2109606-com-matlabobj-feval-works-for-calling-one-function-how-would-it-work-for-calling-a-nested-set

回答： Vatsal 2024-5-7

Take this c# / .NET example of calling a Feval on "cov" for variable t2, which works great:

> t2.GetType()
[System.Double[,]]
> object results = null; matlab.Feval("cov", 1, out results, t2)
> results
object[1] { double[10, 10] { { 32.2, -34.599999999999994, 71.65, 1856.1999999999998, 94.25, 35.45, 92.2, 152.3, -138.3, 157 }, { -34.599999999999994, 2939.7999999999993, 2205.55, 18073.399999999998, -40.24999999999994, 261.15000000000003, 2120.3999999999996, 69.10000000000008, 1741.9, 3924 }, { 71.65, 2205.55, 3813.3, 15569.649999999998, 728.5, 39.14999999999998, 3730.3999999999996, 1317.1, 1380.65, 6561.5 }, { 1856.1999999999998, 18073.399999999998, 15569.649999999998, 395910.19999999995, 7004.25, 6084.450000000001, 17791.2, 13353.3, -6674.299999999999, 34322 }, { 94.25, -40.24999999999994, 728.5, 7004.25, 432.5, 61.750000000000014, 788, 729.5000000000001, -400.75, 1367.5 }, { 35.45, 261.15000000000003, 39.14999999999998, 6084.450000000001, 61.750000000000014, 123.2, 79.19999999999999, 119.8, -135.04999999999998, 189.5 }, { 92.2, 2120.3999999999996, 3730.3999999999996, 17791.2, 788, 79.19999999999999, 3677.2, 1419.8000000000002, 1159.2, 6482 }, { 152.3, 69.10000000000008, 1317.1, 13353.3, 729.5000000000001, ...

This is equivalent to calling:

cov(t2)

How would you call in c# the matlab equivalent of:

cov(cov(t2)) % ?

Obviously, something like this:

> object results = null; matlab.Feval("cov(cov)", 1, out results, t2)
System.Runtime.InteropServices.COMException: Undefined function 'cov(cov)' for input arguments of type 'double'.
  + System.RuntimeType.ForwardCallToInvokeMember(string, System.Reflection.BindingFlags, object, object[], bool[], int[], System.Type[], System.Type)
  + MLApp.MLAppClass.Feval(string, int, out object, object, object, object, object, object, object, object, object, object, object, object, object, object, object, object, object, object, object, object, object, object, object, object, object, object, object, object, object, object, object, object, object)
> 

fails ... what would the syntax be to call this?

Not using .Execute or .Eval on purpose, as calling a function is way better (data does not get publicly available within the global environment, and parallelization is possible within a c# multi-threaded execution environment.

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

Vatsal 2024-5-7

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2109606-com-matlabobj-feval-works-for-calling-one-function-how-would-it-work-for-calling-a-nested-set#answer_1453601

在 MATLAB Online 中打开

Hi Andy,

To "call cov(cov(t2))" from C# using the "Feval" method, it is necessary to approach this in two steps due to "Feval" being able to call only one MATLAB function at a time. Initially, execute the inner 'cov' function and then use its output as the input for the outer 'cov' function.

Here is how you can do it:

Call the 'cov' function on t2 and store the result.
Call the 'cov' function again, but this time on the result from step 1.

Here is an example in C#:

// Call the inner function
object innerResult = null;
matlab.Feval("cov", 1, out innerResult, t2);
// Call the outer function using the result of the inner function
object outerResult = null;
matlab.Feval("cov", 1, out outerResult, innerResult);