trying to convert IDL codes to MATLAB

Hi i'm trying to create a similiar code on matlab to the one i have in IDL

Basically the code lets you select a box_cursor over a region of an image or select the x,y,nx,ny deminsions

the IDL codes are

roichox:
print,'PLEASE SELECT YOUR REGION OF INTEREST: 1=box, 2= enter values'
read,roichoice
case roichoice of
  1: begin
    box_cursor,x,y,nx,ny
    print,"Margins and dimensions:",x,y,nx,ny
  end
  2: begin
    print, 'x?'
    read,x
    ;print, 'y?'
    ;read,y
    print, 'nx?'
    read,nx
    ;print,'ny?'
    ;read,ny
  end
  else: goto, roichox
endcase

my translation so far is

roichoice=input('PLEASE SELECT YOUR REGION OF INTEREST: 1=box, 2= enter values\n');
switch( roichoice)
    case 1
      [I ,rect]=imcrop();
      yb=rect(1);
      xb=rect(2);
      nyb=rect(3);
      nxb=rect(4);    
      fprintf('Margins and dimensions: x=%f y=%f nx=%f ny=%f',xb,yb,nxb,nyb);
    case 2
      xb=input('x?');
      nxb=input( 'nx?');
    otherwise
       goto(roichox);
       return
  end

[John D'Errico]

You used goto? No goto in MATLAB. Try again.

[dpb]

As John says, there is no GOTO in Matlab; leave the otherwise clause empty and enclose the block in a while loop. Use break when get a valid response to exit the block and go on to next step.

Answer 1

[Kris Fedorenko]

As dpb said above, you can use a while loop instead of "goto", which does not exist in MATLAB. Here is one possible example of how you can make it work:

roichoice=input('PLEASE SELECT YOUR REGION OF INTEREST: 1=box, 2= enter values\n');

while ~((roichoice == 1) || (roichoice == 2))
    disp('You must enter either 1 or 2')
    roichoice=input('PLEASE SELECT YOUR REGION OF INTEREST: 1=box, 2= enter values\n');
end

switch( roichoice)
    case 1
        [I ,rect]=imcrop();
        yb=rect(1);
        xb=rect(2);
        nyb=rect(3);
        nxb=rect(4);
        fprintf('Margins and dimensions: x=%f y=%f nx=%f ny=%f',xb,yb,nxb,nyb);
    case 2
        xb=input('x?');
        nxb=input( 'nx?');
end

Hope this helps! And YAY for switching from IDL :)

[hasan alhussaini]

Hi Kris, i was wondering how would you go about changing the code from imcorp to imrect or rbbox?

[Kris Fedorenko]

Hi Hasan,

The difference would be in what these functions return:

• imrect returns a handle to an imrect object. Based on the documentation, you can get the x,y position and dimensions by using a "getPosition" function. For example:

         rectHandle=imrect();
         rect = getPosition(rectHandle);

where rect(1) is x position, rect(2) is y position, rect(3) is width, and rect(4) is height.

• rbbox returns a four-element vector, [x y width height], where x and y are the x and y components of the lower left corner of the box, and width and height are the dimensions of the box. But rbbox returns immediately if a button is not currently pressed. You can use rbbox with waitforbuttonpress, so that rbbox returns when you release the mouse button:

          waitforbuttonpress
          rect = rbbox();

Another difference is that rbboc would define the box in the coordinates of the figure rather than in the axes coordinates.

Hope this helps!

Kris