How do I add a for loop to do subplots

Create a subplot with two graphs subplot(2,1,x). The top plot will be your summed sinusoids and the bottom will show all the sinusoids used to create the final sinusoid. To do this, use the for loop to create a matrix that contains three vectors, one for each of the base sinusoids. Then use one command (outside your function) to plot all three together on the bottom subplot.

My code is below but I am unsure how or where to add a for loop to execute this. My thought was to store the "x" value and then plot it.

function [xx,tt] = syn_sin(fk,xk,fs,dur,tstart)
if nargin <5, tstart=0, end
if length (xk)~= length(fk)
    error ('error', 'fk~=xk');
end
t= tstart: 1/(fs):dur;
x=xk(1)* exp(2*j*pi*fk(1)*t);
for k=2:length(fk);
    x=xk(k) *exp(2*j*pi*fk(k)*t) +x;
end
plot(t,x),grid on    

Answer 1

[Adam Danz]

The general template to build subplots within a loop

nrows = 2; % number of subplot rows
ncols = 1; % number of subplot columns
nsubs = nrows * ncols; % total number of subplots

for i = 1:nsubs
    subplot(nrows, ncols, i)
    plot(. . .)
end

For r2019b or later, you can used tiledlayout

nrows = 2; % number of subplot rows
ncols = 1; % number of subplot columns
nsubs = nrows * ncols; % total number of subplots
tiledlayout(nrows, ncols)

for i = 1:nsubs
    nexttile()
    plot(. . .)
end

Let me know if there are any questions | problems.

[Dalton Houghton-Schaffer]

Would you please be able to explain where my function is having trouble? I as able to get 2 subplots however with an error.

When I go to run this function:

[xx0,tt0] = syn_sin([0,100,250],[10,14*exp(-j*pi/3),8*j],10000,0.1,0);

The error:

Warning: Imaginary parts of complex X and/or Y arguments ignored 
> In syn_sin (line 17)
  In Lab2 (line 112) 
Output argument "xx" (and maybe others) not assigned during call to "syn_sin".

Error in Lab2 (line 112)
[xx0,tt0] = syn_sin([0,100,250],[10,14*exp(-j*pi/3),8*j],10000,0.1,0);
 

Comes up using the program with the loop below:

function [xx,tt] = syn_sin(fk,xk,fs,dur,tstart)
if nargin <5, tstart=0, end
if length (xk)~= length(fk)
    error ('error', 'fk~=xk');
end
t= tstart: 1/(fs):dur;
x=xk(1)* exp(2*j*pi*fk(1)*t);
for k=2:length(fk);
    x=xk(k) *exp(2*j*pi*fk(k)*t)   % +x;
end
nrows = 2; % number of subplot rows
ncols = 1; % number of subplot columns
nsubs = nrows * ncols; % total number of subplots
tiledlayout(nrows, ncols)
for i = 1:nsubs
    nexttile()
    plot(t,x),grid on
    title('SYN SIN')
    xlabel('TIME(sec)')
    ylabel('Frequency')
end 

[Adam Danz]

My bet is that the variable j was not assigned a value. By default, j is an imaginary unit.

[Dalton Houghton-Schaffer]

Thank you so much!!! Yes I always forget to reassign j for i.