i am getting error in this code like "Subscripted assignment dimension mismatch". please tell how to solve it

tic
clc;
r=input('enter the cell radius in meters=');
N=input('enter the no of cells=');

S=3;                                            
x(1)=1;
y(1)=1;
p(1,:)=[x(1),y(1)];
x=zeros(N,2);
y=zeros(N,2);
h=zeros(N,2);
P=zeros(N,1);
for i=2:N
    x(i)=(i-1)*1.5*r;
    h(i)=(i-1)*sqrt(3)*r;
    y(i)=h(i)^2-x(i)^2;
    p(i,:)=[x(i),y(i)];
end  
for i=1:S
    k=randint(1,1,[1 N]);
    P(i,:)=p(k,:);
end
disp(P)

%finding the received signal strength captured by all sensor nodes
theta=2*pi*rand;
X=r*cos(theta);
Y=r*sin(theta);
M=[X,Y];
sum=0;
d=zeros(1,100);
for i=1:S
    for j=1:2
        a=sum+(M(1,j)-P(i,j))^2;
    end
    d(i)=sqrt(a);
end
d0=10;
n=4;
MRSS=-10*n*log(d0);
RSS=zeros(1,100);
t=zeros(100,100);
for i=1:S
    RSS(i)=(MRSS-10*n*log(d(i)/d0))/5;
end
%finding stongest rssi and generating mapping circle
for i=1:S
    d(i)=d0*10^((MRSS-RSS(i))/(10*n));
end
for i=1:S
    for j=1:2
        t(i,j)=(d(i))^2+M(1,j);
    end  
end
[v p]=min(d);
xth =x(p)+d(p)*cos(theta);
yth=y(p)+d(p)*sin(theta);

D(1,:)=[x(p)+d(p)*cos(theta),y(p)+d(p)*sin(theta)];
figure,
plot(t(1:3,1),t(1:3,2),'rs','MarkerEdgeColor','k',...
                'MarkerFaceColor','g',...
                'MarkerSize',4)
            grid on
hold on
xlabel('x co-ordinate of sensor nodes')
ylabel('y co-ordinates of sensor nodes')
legend
plot(D(1,1),D(1,2),'bs','MarkerEdgeColor','k',...
                'MarkerFaceColor','r',...
                'MarkerSize',4)
%results
fprintf('RSSIs collected from 3 sensor nodes=')
disp(RSS)
fprintf('distance of mobile user from all 3 sensor nodes=')
disp(d)
fprintf('co-ordinates of the new location of the mobile user are=')
disp(D)
toc

[Stephen23]

You use nonstandard function randint. The function randint is being obsoleted, and should be replaced with randi.

Answer 1

[Stephen23]

This code has many little "features" that could be simplified, for example:

• try to avoid using both uppercase and lowercase letters for variable names, e.g. p and P.
• x and y are defined rather awkwardly using x(1)=1, y(1)=1). Just use x=1 and y=1 instead.
• many variables are expanded within loops (i.e. without any array preallocation).
• multiple loops could be replaced with much simpler vectorized code (see below).

In any case the problem is very simple: the line P(i,:)=p(k,:) tries to allocate two columns of p to one column of P, thus the "dimensions mismatch" error. Two columns cannot fit into one column.

The best solution is to completely rewrite the whole code using vectorized code, which will be neater, faster and less buggy anyway:

rad = str2double(input('enter the cell radius in meters=','s'));
num = str2double(input('enter the no of cells=','s'));
S = 3;
V = 0:num-1;
p(:,1) = V(:)*1.5*rad;
p(:,2) = (V(:)*sqrt(3)*rad).^2 - p.^2;
p(1,:) = 1;
P = p(randi(num,1,S),:)
disp(P)

[Image Analyst]

Parvez's "Answer" moved here because it's not an answer to the original question.

but after writing ur code it is showing error like "Undefined function or method 'randi' for input arguments of type 'double'".

[Image Analyst]

What version of MATLAB are you using? What does this say

>> which -all randi

[Parvez Halli]

Its Matlab 2007b

[Stephen23]

There seems to have been some changes to randi after that version. Try this line instead:

P = p(randint(1,S,num),:)