multiplication of functions integration problem

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fima v 2020-5-7

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/523738-multiplication-of-functions-integration-problem

编辑： fima v 2020-5-11

采纳的回答： ChrizzzlP

在 MATLAB Online 中打开

Hello,i have two functions "fun" and "coef_fun"

"coef_fun" was created with interpolation of the attached CSV and it looks like in the photo bellow.

I have integrated fun over some interval ,and i got some numeric result.

When i tried to integrate the multiplication of fun and coeff_fun (in order to see the reduction the the numeric result)

It gives me an error "Undefined operator '*' for input arguments of type 'function_handle'"

i have attached my code.

Where did i go wrong in integrating multiplication of functions?

Thanks.

%Default Dataset_new file
data = load('Default Dataset4.csv');
x = data(:,1);
y = data(:,2);
%plot(x,y);
data_x1=x*0.000001; %transform to micron
[data_k, index] = unique(data_x1); 

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Answer 1

ChrizzzlP 2020-5-7

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https://ww2.mathworks.cn/matlabcentral/answers/523738-multiplication-of-functions-integration-problem#answer_430962

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mult_fun needs to be defined as a function too. simple example below:

fun = @(x)x+3;
coef_fun = @(x) 5*x+9;
multiplication_func = @(x) fun(x)*coef_fun(x);
multiplication_func(2)

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fima v 2020-5-7

编辑：fima v 2020-5-11

在 MATLAB Online 中打开

Hello Steven when i did the "fun" ONLY integration,fun_integral results in 43

But when i integrate the element wise multiplication you suggested( which is adding a filter and it should reduce the integral result)instead i get NAN in the mult_integral.

it said "Warning: Infinite or Not-a-Number value encountered"

Why my integral exploded?

What could be done?

Thanks

data = load('Default Dataset4.csv');
x = data(:,1);
y = data(:,2);
%plot(x,y);
data_x1=x*0.000001; %transform to micron
[data_k, index] = unique(data_x1); 