Unable to perform assignment because the indices on the left side are not compatible with the size of the right side.
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Anastasiya Burak
le 8 Oct 2021
Modifié(e) : Anis Syafiqah
le 1 Fév 2023
I have an "unable to perform assignment because the indices on the left side are not compatible with the size of the right side" error when i try to run this code. Could you help how can i solve this problem?
Error in (line 15)
z2(i,j)=f0+A0'*X;
clc;
clear;
a=[0.3; 0.7];
x0=[1; 1];
f0= 2*(a'*x0)+log(a'*x0);
A0= 2+(1/(a'*x0)) ;
B0= -(1/(a'*x0).^2);
x = 0.1: 0.05: 0.5;
[x1,x2] = meshgrid(x,x);
z1 = 2*(a(1,1)*x1+a(2,1)*x2)+log(a(1,1)*x1+a(2,1)*x2);
n=length(x1);
for i=1:n
for j=1:n
X=[x1(i,j)-x0(1,1); x2(i,j)-x0(2,1)];
z2(i,j)=f0+A0'*X;
z3(i,j)=f0+A0'*X+0.5*X'*B0*X;
end
end
colormap(gray);
mesh(x1,x2,z1)
hold on
mesh(x1,x2,z2)
mesh(x1,x2,z3)
xlabel('x1');
ylabel('x2');
hold off
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Réponse acceptée
KSSV
le 8 Oct 2021
Your LHS is a single elememnt and RHS is a 1x2 matrix, which cannot be saved.
May be you want this?
a=[0.3; 0.7];
x0=[1; 1];
f0= 2*(a'*x0)+log(a'*x0);
A0= 2+(1/(a'*x0)) ;
B0= -(1/(a'*x0).^2);
x = 0.1: 0.05: 0.5;
[x1,x2] = meshgrid(x,x);
z1 = 2*(a(1,1)*x1+a(2,1)*x2)+log(a(1,1)*x1+a(2,1)*x2);
n=length(x1);
z2 = zeros(size(x1)) ;
z3 = zeros(size(x2)) ;
for i=1:n
for j=1:n
X=[x1(i,j)-x0(1,1); x2(i,j)-x0(2,1)];
z2(i,j)=f0+A0'*X(1);
z3(i,j)=f0+A0'*X(2)+0.5*X'*B0*X;
end
end
colormap(gray);
mesh(x1,x2,z1)
hold on
mesh(x1,x2,z2)
mesh(x1,x2,z3)
xlabel('x1');
ylabel('x2');
hold off
Plus de réponses (1)
Anis Syafiqah
le 1 Fév 2023
Modifié(e) : Anis Syafiqah
le 1 Fév 2023
I also encounter the same "Unable to perform assignment because the indices on the left side are not compatible with the size of the right side" error. I tried preallocating it by using the zeros for numeric arrays but I still cannot solve it.
The error is at the %Exact Solution part (line 44)
FF(j)=fex(x);
Could somebody help me solve this problem?
% Runge Kutta of order 5
clc
clear
% y''=-4y+2, y(0)=1, y'(0)=1
fy=@(x,y,z) -2;
fz=@(x,y,z) 2-4*y;
fex =@(x) ((1/2*sin(2*x))+(1/2*cos(2*x))+1/2);
x(1)=0;
z(1)=1;
y(1)=1;
h=0.1;
xfinal=1;
N=ceil((xfinal-x(1))/h);
for j=1:N
x(j+1)=x(j)+h;
k1y=fy(x(j),y(j),z(j));
k1z=fz(x(j),y(j),z(j));
k2y=fy(x(j),(y(j)+(1/3*h*k1y)),(z(j)+(1/3*h*k1y)));
k2z=fz(x(j),(y(j)+(1/3*h*k1z)),(z(j)+(1/3*h*k1z)));
k3y=fy(x(j),(y(j)+(2/3*h*k2y)),(z(j)+(2/3*h*k2y)));
k3z=fz(x(j),(y(j)+(2/3*h*k2z)),(z(j)+(2/3*h*k2z)));
k4y=fy(x(j),(y(j)+(h*((-167765027/45900120)*k1y + (43549/7217)*k2y-(30361/14840)*k3y))),(z(j)+(h*((-167765027/45900120)*k1y + (43549/7217)*k2y-(30361/14840)*k3y))));
k4z=fz(x(j),(y(j)+(h*((-167765027/45900120)*k1z + (43549/7217)*k2z-(30361/14840)*k3z))),(z(j)+(h*((-167765027/45900120)*k1z + (43549/7217)*k2z-(30361/14840)*k3z))));
k5y=fy(x(j),(y(j)+(h*((-51638854921283/28366716018615)*k1y + (35525/9169)*k2y - (27646/19955)*k3y- (10643/155037)*k4y))),(z(j)+(h*((-51638854921283/28366716018615)*k1y + (35525/9169)*k2y - (27646/19955)*k3y- (10643/155037)*k4y))));
k5z=fz(x(j),(y(j)+(h*((-51638854921283/28366716018615)*k1z + (35525/9169)*k2z - (27646/19955)*k3z- (10643/155037)*k4z))),(z(j)+(h*((-51638854921283/28366716018615)*k1z + (35525/9169)*k2z - (27646/19955)*k3z- (10643/155037)*k4z))));
k6y=fy(x(j),(y(j)+(h*((-9030268043/1401332565)*k1y + (736810/53619)*k2y - (28702/5227)*k3y- (7/5)*k4y +(3/5)*k5y))),(z(j)+(h*((-9030268043/1401332565)*k1y + (736810/53619)*k2y - (28702/5227)*k3y- (7/5)*k4y +(3/5)*k5y))));
k6z=fz(x(j),(y(j)+(h*((-9030268043/1401332565)*k1z + (736810/53619)*k2z - (28702/5227)*k3z- (7/5)*k4z +(3/5)*k5z))),(z(j)+(h*((-9030268043/1401332565)*k1z + (736810/53619)*k2z - (28702/5227)*k3z- (7/5)*k4z +(3/5)*k5z))));
y=zeros(size(k6y));
z=zeros(size(k6z));
y(j+1)=y(j)+(h/144)*((14*k1y)+(48*k2y)+(162*k3y)+(33*k4y)-(125*k5y)+(12*k6y));
z(j+1)=z(j)+(h/144)*((14*k1z)+(48*k2z)+(162*k3z)+(33*k4z)-(125*k5z)+(12*k6z));
%Exact solution
FF(j)=fex(x);
xx(j)=x;
%Error
Err(j) = abs(FF(j)-y(j));
fprintf('%.1f\t\t%7.8f\t\t%7.8f\t\t%7.8f\n', xx(j), FF(j), y(j), Err(j))
end
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