MATLAB: Is the code not working

wrong code

I need to plot a graph of error_d against a. a is changing by 10 units from 0 to 1000 so thats why I used a for loop. My code is the following: for a=1:10:1000 A_n=((-3)^-a)/(2*a+1); D_n= A_n*sqrt(12); error_d= abs(pi-D_n); axis([0 1000 0 1]); plot(a,error_d); end

but this is not showing any graph. I donot know what is wrong. Can anyone help me?

Best Answer

It is not showing a plot because ‘error_d’ is not in the range you believe it to be. Also, it is much more efficient to take advantage of MATLAB’s ability to vectorise expressions.

The Code —

a=1:10:1000;
A_n=((-3).^-a)./(2*a+1);
D_n= A_n*sqrt(12);
error_d= abs(pi-D_n);
figure(1)
plot(a,error_d);
axis([0 1000 ylim])

This will produce the plot.

Related Solutions

MATLAB: How to fit the data by using lsqcurvefit

I didn't exactly understand how you went from your function to the code, so I re-implemented it. Apparently there is a functional difference, because this code does run correctly. One of the changes I made is calculating the sum as a stand-alone array. This does use implicit expansion, so if you're using R2016a or earlier you need to expand the arrays yourself first.

xdata=[0;86400;259200000;604800000;12096000000.0000;24192000000.0000];
ydata=[1.06180000000000;0.498230000000000;0.270470000000000;0.225110000000000;0.229290000000000;0.251620000000000];
x0=[1*10^-10,3];
x = lsqcurvefit(@sorptio,x0,xdata,ydata);
function ydata=sorptio(x,xdata)
D=x(1);
h=x(2);
t=xdata(:);%force nx1 size
n=0:1000;
S=(2*n+1).^(-2) .* exp( (-(2*n+1).^2 * pi^2 * D .*t)/(h^2) );
S=sum(S,2);
ydata=1-S*8/(pi^2);
ydata=reshape(ydata,size(xdata));%return to original size
end