Debugging code via println is a tried and true way to debug/evolve your code. Inside draw() add

puuh!!

difficult it was

1. int[] RCTime = {
2.   1800, 1500
3. };
4. //  RCTime[0] = 1800;
5. //  RCTime[1] = 1500;
6. //int i=6;
7. boolean growing=true;
8. //
9. //
10. void setup() {
11.   size(300, 500);
12. } // func
13. //
14. //
15. void draw() {
16.   background(255);
17.   fill(0);
18.   rectMode(CENTER);
19.   if ( growing ) {
20.     if (RCTime[1]>=2300) {
21.       growing=false;
22.     }
23.   }
24.   else {
25.     // growing is false
26.     if (RCTime[1]<=400) {
27.       growing=true;
28.     }
29.   } // else
30.   // now eval "growing"
31.   if (growing) {
32.     RCTime[1]=RCTime[1]+25;
33.     //i++;
34.   }
35.   else
36.   {
37.     RCTime[1]=RCTime[1]-25;
38.     // i--;
39.   }
40.   // draw the beast
41.   rect(150, 250, 30, RCTime[1]/10);
42. } // draw
43. // ---------------------------------------

jas, thank you for the pointer, I had tried i=i+1;, but that didn't help either, changing my code w/ your reccomendations did not make it work though.  I realize I should have while loops, so here is my current code.

1.   int[] RCTime = {180, 150};
     int i=0;
    
   void setup(){
     size(300,500);
   }
   
   void draw(){
   
     background(255);
     fill(0);
     rectMode(CENTER);
   
     while(i<6){
       rect(150,250,30,RCTime[1]/10); 
       RCTime[1]=RCTime[1]+25;
       i++;
     }
     while(i>1){
       rect(150,250,30,RCTime[1]/10); 
       RCTime[1]=RCTime[1]-25;
       i--;
     }
   }

remember that draw() runs in a loop in itself (about 60 times per second - fast). You can stop that automatic loop with noLoop(). But that's not a good idea for you here, because thus you see no movement at all but just the finished static picture.

Thus the "while" doesn't help you here, he is only drawing once at the end of draw() anyway.

So I think your questions are all answered with Yes :

the while loop loops without calling draw?

Yep.

does the screen only refresh once when draw is called

Yep. At the end of draw(). Automatically.

changing rect does not change the image I see?

Yep. Unless you make sure the rect is changed (compared to the last time you ran draw()) when the end of draw is reached.

Keep up your spirit!  

hm...

Remember that draw runs 60 times or so every second. Thus (you need no while and) concerning "i" you need values like 90 because with 4 it's too fast to see... (make it slower with     frameRate(12);  as I did).

I tried again with your approach - he stutters when reaching the longest length... (other than in my working program above)

That's because when he is over 90, i gets smaller by 1 (i--;) and i is then again smaller than 90 and i gets increased by 1 (i++) and thus he stutters at i around 90... and so does your rect.

But at last it's growing now first...

1. int[] RCTime = {
2.   180, 150
3. };
4. int i=0;
5. void setup() {
6.   size(300, 500);
7. }
8. void draw() {
9.   background(255);
10.   fill(0);
11.   rectMode(CENTER);
12.   if (i<90) {
13.     RCTime[1]=RCTime[1]+25;
14.     i++;
15.   }
16.   else if (i>10) {
17.     frameRate(4);
18.     RCTime[1]=RCTime[1]-25;
19.     i--;
20.   }
21.   println (i);
    
22.   rect(150, 250, 30, RCTime[1]/10);
23. }