Loops in Matlab + Multiple Plots

Hi, I'm new to MATLAB, I have a piece of code that is working that takes computed currents of linear antennas and plots them, it looks like: (each antenna is divided into M pieces)

I1=abs(I(M+1:end,1)); z1=z(M+1:end,1);

I2=abs(I(M+1:end,2)); z2=z(M+1:end,2);

I3=abs(I(M+1:end,3)); z3=z(M+1:end,3); etc.

figure; plot(z1,I1,'.'); figure; plot(z2,I2,'.'); etc.

What I want to do is automate this for an arbitrary number of antennas. I have had several trials of the sort:

for j=1:N

I_(j)=abs(I(M+1:end,j)); z_(j)=z(M+1:end,j);

end

..or, I_j, or I(j) .. but as it became clear, I need to understand first what's going on in this (M+1:end,1) statement, and why do I get errors when I try any of the trial codes above.

1st type of error, for I_(j) and I(j)

??? In an assignment A(I) = B, the number of elements in B and I must be the same.

Error in ==> VB_Array25 at 18 I_(j)=abs(I(M+1:end,j)); z_(j)=z(M+1:end,j);

2nd type is when I use I_j, it doesn't say anything about the for loop but when I try figure; plot(z_1,I_1,'.');

??? Undefined function or variable 'z_1'.

Error in ==> VB_Array25 at 29 figure; plot(z_1,I_1,'.');

Any help will be more than welcome. -----------------------------------------------------

What I basically want to do after this, is be able to make all plots of I(z) for an arbitrary number of antennas on one plot and I will appreciate any comments on this as well.

Answer 1

[Matt Fig]

Use cell arrays.

for jj=1:N
   Ic{jj} = abs(I(M+1:end,jj)); 
   z{jj} = z(M+1:end,jj);
   figure
   plot(z{ii},Ic{ii})
end

As for the (M+1:end,jj) statement, this just means to take the M+1 through last rows, and the jjth column. You might also want to take a look at the SUBPLOT function, rather than making all those figures.

[Victor Buza]

Thanks, that worked.

I have taken a look at Subplot but it seems that it can only fit 4 plots at once, is there a way to fit any number?

[Matt Fig]

I don't know where you got that idea. From the help for SUBPLOT (first line in fact) -

H = SUBPLOT(m,n,p), or SUBPLOT(mnp), breaks the Figure window

into an m-by-n matrix of small axes, selects the p-th axes for

the current plot, and returns the axis handle.

Did you read the help for SUBPLOT??

[Victor Buza]

I am sorry, that was a stupid decision to look else than the help files, I swear I read somewhere that it does only 2x2. Thanks.