# Error using sym/subsindex

7 views (last 30 days)
Susmit Kumar Sahu on 9 Jul 2020
Answered: Devineni Aslesha on 22 Jul 2020
I need to make this code work.
Trying for 2 days, Please someone help me to debug this error.
Error displayed
clc
clear
Start = input("Enter the Start value: ");
End = input("Enter the End value: ");
grid_size = input("Enter the grid size: ");
np = input("Enter the number of input points: ");
x = zeros(1,np,'uint32');
y = zeros(1,np,'uint32');
i = 1;
while i <= np
x(i) = input("Coordinates of X value: ");
y(i) = input("Coordinates of y value: ");
i = i + 1;
end
j = 1;
px = zeros(1,np);
py = zeros(1,np);
syms j
for t =0:1:0.01
blending_function = (factorial(np)/factorial(j)*factorial(np-j)).*(t.^j).*(1-t).^(np-j))
px = symsum((blending_function.*x(j+1),j,0,np-1);
py = symsum(((factorial(np)/factorial(j)*factorial(np-j)).*(t.^j).*(1-t).^(np-j)).*y(j+1),j,0,np-1);
end
%px=(1-t).^3*x(1)+3*t.*(1-t).^2*x(2)+3*t.^2.*(1-t)*x(3)+t.^3*x(4);
%py=(1-t).^3*y(1)+3*t.*(1-t).^2*y(2)+3*t.^2.*(1-t)*y(3)+t.^3*y(4);
title("Bezier Curve for cloud points")
grid on
grid minor
plot(x,y);
hold
plot(px,py,'r');
xlabel('postition in x');
ylabel('position in y');
legend('Actual curve','Bezier Curve');
%axis([0 4.2 0 3.2]);
Susmit Kumar Sahu on 9 Jul 2020

Devineni Aslesha on 22 Jul 2020
Hi Susmit
In the given code, the error is due to the presence of x(j+1) and y(j+1) that belongs to Class uint32. However, the Expression defining terms of series in symsum should be symbolic (Class: sym). Make sure what is the purpose of using x and y in your code and convert it to symbolic expression. If you remove x(j+1) and y(j+1), the code runs without any error.

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