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I am having problems in anonymous function (y=@(x)(...))

Asked by Angus Wong on 29 Apr 2019
Latest activity Edited by Angus Wong on 1 May 2019
Let me re-word my querry.
Let's say there is a square matrix of v=[1 2 3 4 5 6 78 9 10; 11 12 13 14 15 16 17 18 19 20;21 22 23 24 25 26 27 28 29 30;31 32 33 34 35 36 37 38 39 40;41 42 43 44 45........ 99 100] and a is a variable that prompt the user to input. It is easy to obtain a square matrix of size a by a of the original matrix v (left hand corner) with the use of w=v(1:a,1:a), of course a is less than length(v).
However, I would like to know how to do the same for anonymous functions. v in this case will be a column matrix a quantities of "@(x)(B.*[x x^2 x^3 ......]);", where [x x^2 x^3 ......] is a row matrix with a elements.
Here is an example:
Let's say v={@(x)([x x^2 x^3 x^4]; @(x)([x^2 x^3 x^4 x^5]); @(x)([x^3 x^4 x^5 x^6]); @(x)([x^4 x^5 x^6 x^7])};
if a = 3, the new v would be v={@(x)([x x^2 x^3]; @(x)([x^2 x^3 x^4]); @(x)([x^3 x^4 x^5])};

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Oh, there supposed to be sum() there, my copy and paste skills should improve. Let me change that. But the program still doesnt work.
ok, just wanted to make sure. Also, what is x supposed to be? I think maybe it'll be easier to construct the matrix if x was an input to your function fun, instead of creating so many anonymous functions.
x is a variable.
The script is something like this:
clear; close all; clear;
dat=load(data);
leadingcoe=coef(dat);
yo=fun(leadingcoe);
k=input('Input a number for x');
for a=1:k
disp(yo{a}(k));
end
This is a simplified version.

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1 Answer

Answer by Kevin Phung on 29 Apr 2019
Edited by Kevin Phung on 29 Apr 2019

let me know if this is what youre trying to do with your anon functions:
function y = fun(a,x)
y = sum(triu(repmat(flip(x.^(1:a)),numel(a),1)),2)
%uncomment this if you want to see how the matrix looks like before summing the rows
%y = triu(repmat(flip(x.^(1:a)),numel(a),1))
end

  3 Comments

Emmm. Sorry. No, this is not I am looking for. Let's say a=[1 2 3 4 5];
I am expecting the output to be:
y={@(x)(sum(a.*[x x^2 x^3 x^4 x^5]));
@(x)(sum(a.*[0 x x^2 x^3 x^4]));
@(x)(sum(a.*[0 0 x x^2 x^3]));
@(x)(sum(a.*[0 0 0 x x^2]));
@(x)(sum(a.*[0 0 0 0 x]))};
After this, in the main script, I then define a numerical value to the variable x (let's say 6) and display the result. I expect the final output from the main script to be [44790;7464;1242;204;30].
44790 comes from 1*6+2*6^2+3*6^3+4^6^4+5*6^5.
I then am able to change the value assigned to x and get a new vector.
Hence, my x is not defined as a numerical value inside the anonymous function, but a variable.
Basically my intended program steps are: import the data set, determine the number of columns using size(,2), running the anonymous function (fun) with the leading coefficients as the sole input and output a set of anonymous functions based on that, able to set a numerical value for the variable x and output the results for the anonymous functions based on the vzalue of x as a column vector.
This function is intended to output an anonymous function.
But thanks a lot for your hard work!

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