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

Asked by Angus Wong

Angus Wong (view profile)

on 29 Apr 2019
Latest activity Edited by Angus Wong

Angus Wong (view profile)

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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Angus Wong

Angus Wong (view profile)

on 29 Apr 2019
Oh, there supposed to be sum() there, my copy and paste skills should improve. Let me change that. But the program still doesnt work.
Kevin Phung

Kevin Phung (view profile)

on 29 Apr 2019
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.
Angus Wong

Angus Wong (view profile)

on 29 Apr 2019
x is a variable.
The script is something like this:
clear; close all; clear;
k=input('Input a number for x');
for a=1:k
disp(yo{a}(k));
end
This is a simplified version.

Release

R2019a

Answer by Kevin Phung

Kevin Phung (view profile)

on 29 Apr 2019
Edited by Kevin Phung

Kevin Phung (view profile)

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

Angus Wong

Angus Wong (view profile)

on 29 Apr 2019
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.
Angus Wong

Angus Wong (view profile)

on 29 Apr 2019
This function is intended to output an anonymous function.
Angus Wong

Angus Wong (view profile)

on 29 Apr 2019
But thanks a lot for your hard work!