MATLAB: Subscript indices must either blabla

>> gamma=0;
>> s=0;
>> dx=linspace(0,10);
>> dx=0.1;
>> xv=linspace(0,10);
>> f=@(x) sin(2*pi*x/10);
>> xnodes=(0:0.1:10-0.1);
>> f=adr_per_cen_fd(0,f(xnodes),u,ni,gamma,s,xnodes,dx);

SUBSCRIPT INDICES MUST BE POSITIVE OR REAL, UHM. can you help me?

Thank you

Best Answer

What is adr_per_cen_fd? It thinks it is an array, not a function and if its an array, all the dimensional indexes must be integers. You can't have the 0.1th column of a matrix.

Related Solutions

MATLAB: How to plot 3D curves with for loop

In the 'for' command you write:

for v=0:1:20

which means that on each trip through the loop 'v' will be a scalar quantity - that is, a single number. When you do

[Xd,Xq]=meshgrid(v,v);

that destroys the Xd and Xq you computed just before that and creates scalar values for Xd and Xq instead, both equal to the scalar v. Therefore the command

surf(Xd,Xq,F)

has only one point which is not a very effective surface plot. Moreover, since you are not activating the "hold on" command, each plot overwrites the previous one.

If you want to plot a surface using 'surf' (which is different from plotting a 3D curve) you should not be using the for-loop. Instead just write

v = 0:20;
[Xd,Xq] = meshgrid(v,v); % <-- You can also use just meshgrid(v)
% Calculate F using Xd and Xq (which will be 41 x 41 matrices)
surf(Xd,Xq,F)

If on the other hand you really do want to plot a 3D curve, you should be using the 'plot3' command, not 'surf', and you should generate F in terms of a single vector, presumably 'v'.

MATLAB: Error of Subscript indices must either be real positive integers or logicals, index exceeds matrix dimension,

There may be multiple error, I have noticed one immeditely

You have defined dt1 as

dt1=dx1/(a1*n);

It return the value

dt1 =
   0.050000000000000

Again

You have defined v1 as following, which is scalar

>> v1=4*Q/(pi*dia1^2)
v1 =
   0.254647908947033

At the last line (Numerator) calling the v1 as vector

   *v1(2,t+dt1)
   %at initial t define as 
   t=0;

What does it mean? See it becomes v1(2,0+0.05) , which goes to v1(2,0.5)

Here two issue

As your v1 is scalar based on the data as you have defined, there is no menaing of v1(?,?)
If v1 is vector, please ensure that v1(r,c), these r and c values always greater that 0 (real positive) within the specified rannge,

If r and c are not real and positive integers than Matlab shows the error

error of Subscript indices must either be real positive integers or logicals

And if the r and c value out of range (dimension), Matlab shows the error-

index exceeds matrix dimension.

Please debug the code step by step and find the issue. Indeed this is easy, hope you can do it.

Good Luck & Hope it Helps!

Best Answer

Related Solutions

MATLAB: How to plot 3D curves with for loop

MATLAB: Error of Subscript indices must either be real positive integers or logicals, index exceeds matrix dimension,

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