How to fix the unrecognized error??

In the following code, runtime error of "Unrecognized function or variable 'cbar'." is popping up. The code is trying to plot the mean of normal customer in interjecting queuing system. Kindly look into it.

Thanks and Regards

Arsh Tyagi

m = 40;
a = 2.0;
th = 0.2;
x = 0.5:0.001:1.5;
for n=1:m-1
    for k=2:n+1
        for l=k:n
            for i=k-1:l-1
                for j=1:i
                    d1 *= exp(-1/j);
                end
                a1 *= (1-d1);
            end
            b1 += (((x./a).*th).^(l-k+1)).*a1;
        end
        cbar += b1;
    end
    x2 += ((x/a).^n)*cbar;
end
for k=2:m
    for l=k:m
        for i=k-1:l-1
            for j=1:i
                d1 *= exp(-1/j);
            end
            a1 *= (1-d1);
        end
        b1 += (((x./a).*th).^(l-k+1)).*a1;
    end
    x3 += b1;
end
y2 = y1+x2+((1-x/a).*(((x/a).^m)./(a.*(1-(x/a).^(m+1))).*x3));
plot(x,y2);

[KSSV]

You code looks like a C code......Note that there is no possibility to use:

a1 .* = 
cbar .+ = 

You need to copy and paste your code here so that people can help you here. By adding code as image snippet, one cannot run the code to help you.

[Walter Roberson]

cbar += b1;

MATLAB would treat that as

cbar('+=', 'b1')

MATLAB does not have any of the op= operators such as += or &=