error index exceeds dimensions

hello, i'm new in MATLAB, i want to ask,, i have an image and i already transform them into binary image the image is like this :

i want to convert my binary image become straight line

here is the code :

global X;
X = handles.m;
X = gca;
global freq;

X.Scale = 'log';
  int X p1 p2;
  double froot(301),freq(301),val(301),point(301);
  double val1 val2; result; %#ok<VUNUS,NODEF>

    for X=0; X<301; %#ok<VUNUS>
      froot(X) = 8e-3 + (100e-3)/301.0*X; %#ok<AGROW>
      freq(X)  = (1.0/froot(X))*(1.0/froot(X)); %#ok<AGROW>
      point(X) = 301.0*freq(X)/20000.0; %#ok<AGROW>
        p1 = trunc(int(point(X)));
        p2 = p1+1;
        val1 = val(p1);
        val2 = val(p2);
        result = val1+(val2-val1)/(p2-p1)*(point(X)-p1); %#ok<NASGU>
    end
  guidata(hObject,handles);
  axes(handles.axes3);
  imshow(X);
  msgbox('Transform SUCCESSFUL !');

but when i execute the program,, an error message appear like this :

??? Index exceeds matrix dimensions.

Error in ==> processing>pushbutton10_Callback at 177
  double froot(301),freq(301),val(301),point(301);

i can't figure it out where the problem was,, i need help

Thanks

[KSSV]

Check dimensions of froot,freq,val,point they must be less then 301 and you are accessing 301 index of those.

[Evan Weking]

oh i see, okay i'll try it..

thanks for your suggestion

Answer 1

[Walter Roberson]

MATLAB does not declare variables. Your line

    double froot(301),freq(301),val(301),point(301);

is instead a call to double() followed by a series of other commands, and is equivalent to

    double( 'froot(301)' )
    freq(301)
    val(301)
    point(301);

[Evan Weking]

thanks for your answer,, i fixed my code just like you suggest, but another error message appeared like this :

??? Attempted to access freq(301); index out of bounds because numel(freq)=0.

Error in ==> processing>pushbutton10_Callback at 178
  freq(301)

is it means that i must change freq index value to 0 ? thanks

[Walter Roberson]

In MATLAB,

      for X=0; X<301; %#ok<VUNUS>

is the same as

      for X=0
        X<301;   %do a logical test and throw the result away because the semi-colon says not to print it
      ...

If you want a loop from 0 to 300 you need

    for X = 0 : 300

Remember though that MATLAB indexing starts at 1