Question

I’m currently translating code from Fortran to MATLAB manually, and I am unsure of how to translate part of it. (The entire code actually is a 2,000 line subroutine.) The code is below.

C  Has series crossed neckline?
120        neckext=x(trough(peaknum-1))+
 *              dydx*real((t-trough(peaknum-1)))


        if(x(t).lt.neckext) goto 130
C      NO.  Here if series has not crossed neckline, nor new trough found
C           Check to see if new trough has been found.
        t=t+1
        if(t.ge.lastobs) goto 900
        if(x(t).lt.min) then
              min=x(t)
              mindate=t
              end if
        troughid=min*(1.0+cutoff)
        if(x(t).ge.troughid) goto 150
        goto 120

C      YES. Here if series crossed neckline before new trough found
130         dblcount=0
      if(poscount.ge.1) then
          DO 132 i=1,poscount
           if((enterdt(i)-2.le.t).and.(t.le.enterdt(i)+2)) then
           dblcount=dblcount+1
           end if    
132          continue
           if(dblcount.ge.1) then
C                write(30,2583) t,Cutnum
2583            format('DoubleCounting episode occurred at ',I5,
 *             ' with Cutoff = ',F3.1)
            goto 150
          end if
       end if

My problem is with this part of the code:

        if(x(t).ge.troughid) goto 150
        goto 120

When I was translating this part in MATLAB, I was writing something like:

if x(t,:)>=troughid
    t=marker;
    minimum=x(t,:);
end

But I don’t know what to do with the label 120. When I translate it, do I write that part again? Because from what I understand, when I go back to 120, the code will be running again. Thanks!

EDIT: As a response to Chris’s question on what labels 150 and 900 do, I’ll post them here.

150        t=marker
           min=x(t)

And this is for the label 900.

C  Last observation found.  This iteration finished.
900        continue

Answer 1

As it should be clear by now, Matlab does not include any variant of a “goto” command. The core Matlab command set appear to be designed around the “structured programming” philosophy. (Which, if I remember my CS ancient history correctly, was the great debate prior to object oriented programming.) Wikipedia has a decent discussion of structured programming.

In the dark days before structured programming, people used to be very excited about flow charts, since that was one of the easiest ways to visualized and understand a piece of code using a lot of goto statements (now usually referred to as spaghetti code).

I suspect that you will need to flowchart the entire subroutine, and then decide which control flow constructs can best be used to recreate your code. If it is a relatively simple diagram, then you should be able to recreate the entire code with if statements or case statements, although a series of small helper functions may be more elegant. If it has a more complex structure, then it may take a little more creativity to translate.