"Matrix dimensions must agree" when trying to plot the sum of a sin function

x=[-pi:pi/100:2*pi]

x = 1×301

-3.1416 -3.1102 -3.0788 -3.0473 -3.0159 -2.9845 -2.9531 -2.9217 -2.8903 -2.8588 -2.8274 -2.7960 -2.7646 -2.7332 -2.7018 -2.6704 -2.6389 -2.6075 -2.5761 -2.5447 -2.5133 -2.4819 -2.4504 -2.4190 -2.3876 -2.3562 -2.3248 -2.2934 -2.2619 -2.2305

figure
for n=20
    m = (1:n).';
    s2 = sin((2*m-1)*x)/(2*m-1);
    plot(x,s2, 'displayname', "\alpha = " + n);
    hold on
end

Error using /
Matrix dimensions must agree.

legend show

I get this error when I'm trying to plot for n = 20

What did I do wrong?

[Dyuman Joshi]

What exactly are you trying to plot?

Is n just equal to 20 or is it equal to 20 * (sum of the series) ?

[Jordi van Selm]

n=20 and I would only want to get the function for the sum until n=20

Answer 1

[VBBV]

s2 = sin((2*m-1)*x)./(2*m-1);

Use element wise division

[VBBV]

x=[-pi:pi/100:2*pi]

x = 1×301

-3.1416 -3.1102 -3.0788 -3.0473 -3.0159 -2.9845 -2.9531 -2.9217 -2.8903 -2.8588 -2.8274 -2.7960 -2.7646 -2.7332 -2.7018 -2.6704 -2.6389 -2.6075 -2.5761 -2.5447 -2.5133 -2.4819 -2.4504 -2.4190 -2.3876 -2.3562 -2.3248 -2.2934 -2.2619 -2.2305

figure
for n=20
    m = (1:n).';
    s2 = sin((2*m-1)*x)./(2*m-1);
    plot(x,s2, 'displayname', "\alpha = " + n);
    hold on
end
legend show

[Dyuman Joshi]

It seems for loop is not required and it should be m instead of n in the plot command.

[Jordi van Selm]

Thanks, but how do I get to see the value for n=20 only?

[VBBV]

The given figure is obtained for value of n = 20. Do you mean when last value of m ? summation of s2

x=[-pi:pi/100:2*pi]

x = 1×301

-3.1416 -3.1102 -3.0788 -3.0473 -3.0159 -2.9845 -2.9531 -2.9217 -2.8903 -2.8588 -2.8274 -2.7960 -2.7646 -2.7332 -2.7018 -2.6704 -2.6389 -2.6075 -2.5761 -2.5447 -2.5133 -2.4819 -2.4504 -2.4190 -2.3876 -2.3562 -2.3248 -2.2934 -2.2619 -2.2305

figure
n=20

n = 20

m = (1:n).';
s2 = sin((2*m-1)*x)./(2*m-1);    
plot(x,sum(s2,1), 'displayname', "\alpha = " + n);   
legend show

[Jordi van Selm]

Is this the function that I get when I add sin((2*1-1)*x)/(2*1-1) + sin((2*2-1)*x)/(2*2-1) + ... + sin((2*20-1)*x)/(2*20-1) ?

EDIT; Yes, I check on Desmos. Thanks!

[VBBV]

Yes. You get the summation of the expression for values upto 20.

[Jordi van Selm]

Thanks again. My last job was to merge two function to get:

x=[-pi:pi/100:2*pi]

x = 1×301

-3.1416 -3.1102 -3.0788 -3.0473 -3.0159 -2.9845 -2.9531 -2.9217 -2.8903 -2.8588 -2.8274 -2.7960 -2.7646 -2.7332 -2.7018 -2.6704 -2.6389 -2.6075 -2.5761 -2.5447 -2.5133 -2.4819 -2.4504 -2.4190 -2.3876 -2.3562 -2.3248 -2.2934 -2.2619 -2.2305

figure
n=20

n = 20

m = (1:n).';
s1 = (1/m*sin(m*x));
s2 = sin((2*m-1)*x)./(2*m-1); 
plot(x,sum(s1,1),x,sum(s2,1), 'displayname', "\alpha = " + n);   
legend show