How can I multiply equation with number

Question

Eman Ahmed Elsayed 2011-5-31

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/8544-how-can-i-multiply-equation-with-number

I need to multiply a number by an equation

function [result] = SA_1(func,lamda)
%UNTITLED Summary of this function goes here
%   Detailed explanation goes here
syms a;
a=lamda;
f=a*func;
result=f;
 end

when I run I get the following error

??? Undefined function or method 'mtimes' for input arguments of type 'function_handle'.
 Error in ==> SA_1 at 6
 f=a*func;

I need any help

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Answer 1

daniel.x16 2011-5-31

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put a dot (.) before the * sign.

i.e. f=a.*func

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Eman Ahmed Elsayed 2011-5-31

no that's solved the problem

Walter Roberson 2011-5-31

I doubt that. All that would do is change the error message from being about 'mtimes' to being about 'times'.

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Answer 2

Walter Roberson 2011-5-31

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https://ww2.mathworks.cn/matlabcentral/answers/8544-how-can-i-multiply-equation-with-number#answer_11763

在 MATLAB Online 中打开

Your line "a=lambda" overwrites the "syms a" that was established on the line above. You probably do not need the "syms a".

What you probably want is

function [result] = SA_1(func,lamda)
  result=@(x) lambda*func(x);
end

This will construct a new function handle that includes the multiplication.

Warning: you won't be able to differentiate the new function handle either. Only symbolic expressions can be differentiated by MATLAB, unless you write the differentiation yourself.