"index exceeds matrix dimensions" when using str2double

Hi guys.

I am currently attempting to receive data from Arduino and saving them into a Matlab array. I'm not sure why, but I got stuck in an error "index exceeds matrix dimensions" while trying to save str2double value into an array location. I'm wondering if this is because I'm not allowed to save any double values into an array? How should I come across this :( Below I've attached my code.

Thanks in advance.

//////////////////////////////////////

clc

clear s

delete(instrfindall);

%initializing port connection

s=serial('COM7','BaudRate',9600,'DataBits',8);

s.StopBits=1;

fopen(s);

%receiving text info from COM7

n=10;

array=zeros(n,3);

for i=1:n

fprintf(s,'*IDN?');

answer = fscanf(s)

angle=textscan(answer,'%c %s %s %s %c');

array(i,1)=str2double(angle{i,3});

array(i,2)=str2double(angle{i,4});

array(i,3)=str2double(angle{i,5});

end

%converting string info to double and saving them into array

fclose(s);

delete(s)

clear s

[KSSV]

What is size(angle) ? before and after str2double?

[Jan]

@Jaz: Please post the complete error message, such that the readers do not have to guess, in which line the error occurres.

[Heejin Kim]

Oops pardon. The error has occured on

array(i,1)=str2double(angle{i,3});

[Heejin Kim]

@KSSV Sorry I am not quite sure what you mean by "before and after", but the angle info from arduino is a 1×5 vector, from which I needed the 3rd, 4th, and 5th string value.

[Jan]

@Jaz: See my answer: Then you need "angle{3}" and not "angle{i,3}".

Answer 1

[Jan]

Text scan replies a cell vector as output. Therefore the first index "angle{*i*, 3}" is misplaced:

for i=1:n
  fprintf(s,'*IDN?');
  answer = fscanf(s)
  angle  = textscan(answer,'%c %s %s %s %c');
  array(i,1) = str2double(angle{3});  % instead of "angle{i,3}"

The output of textscan will not depend on the loop counter i.

 I'm wondering if this is because I'm not allowed to save any double
 values into an array?

On one hand it is wise to use phantasy to examine different possible sources of problems. On the other hand, speculations are less useful as the debugger. Type this in the command window:

dbstop if error

or use the corresponding menu of the editor. Then run the code until it stops in the failing line. Now check the details in the command window:

% Failing line: array(i,1)=str2double(angle{i,3});
size(angle)
class(angle)
i
angle{i,3}
str2double(angle{i,3})
which('str2double')   % function shadowed by a variable?

Using the debugger is more efficient than asking the forum.

[Heejin Kim]

Thanks for the solution & advice!!