How do I generate a random set of integers for an array (which determines endpoints for various lines) ONCE, and then when keyPressed, I can regenerate a new set of random integers?

I've created a function called LinearDeformation, and through a series of calculations I determine the endpoints for "major segments" which have a certain X range and Y range according to the width and height of the display. The random function determines a point within the determined ranges. 

At the moment, the random function is continuously looping. I don't want to use noLoop(); because I want to be able to adjust the "margChange" continuously by pressing the arrow keys (and have real-time feedback). I've tried creating a separate function for integer generation but I'm having trouble figuring out how to structure it.

Here is the code, sorry if its illegible:

2. float YmarginX= 20;
3. float XmarginX = 20;
4. float YmarginY= 20;
5. float XmarginY = 20;
6. 
   
7. 
   
8. float margChange = 1;
9.   
10.   
11.   float[] start;
12.   float[] range;
13.   float[] end;
14. 
    
15. 
    
16. 
    
17. 
    
18. 
    
19. void setup(){
20.   
21.   size (500,500);
22. 
    
23.   smooth();
24. //noLoop();
25.   randomSeed(0);
26. //regenValues(Xmargin, Ymargin);
27. 
    
28. }
29. 
    
30. 
    
31. 
    
32. void draw(){
33.     background(255);
34.   
35. 
    
36.   
37.   
38.   //  X directionality 
39.  strokeWeight(3);
40.   LinearDeformation(XmarginX, YmarginX, margChange);
41.    
42.  //  Y directionality
43.    
44. strokeWeight(5);
45.    pushMatrix();
46.    translate(0,500);
47.    rotate(radians(270));
48.     LinearDeformation(XmarginY, YmarginY, margChange);
49.    popMatrix();
50.   
51.   
52. 
    
53.   }
54.  // */
55.   
56. 
    
57. 
    
58. 
    
59. void keyPressed(){
60.   
61.   if (keyPressed){
62.   
63.   if (keyCode == LEFT ){
64.     if (margChange>0.1){
65.    margChange=margChange-(0.1);
66.     }
67.        
68.   }
69.   
70.    
71.      if (keyCode == RIGHT ){
72.        
73.    if (margChange<4.9){
74.    margChange=margChange+(0.1);
75.     }
76.        
77.   }
78.       
79.        
80.   
81.   if (key==' '){
82.     
83.       redraw();
84.     }
85. 
    
86. 
    
87. 
    
88. }
89.   
90.     
91.     
92.  }
93. 
    
94. 
    
95.   
97. void LinearDeformation (float Xmargin, float Ymargin, float margChange) {
98.   
99. int numReps=5;
100.   float[] start = new float[numReps];
101.   float[] range = new float[numReps];
102.   float[] end = new float[numReps];
103.   
104.    float NEWheight = height-(2*Ymargin);
105. 
     
106.   
107.   
108. //arrays for enpoint placement  
109.   
110. for (int s = 0; s < numReps; s++){
111.     if (s < 3){
112.         start[s] = random(Xmargin, ( ((s*.1)+.1) *width ));
113.     } 
114.     
115.     else {
116.         start[s] = random(Xmargin, ( ((3-(s-2))*.1) *width ));
117.     }
118.   }
119.     
120.     
121.     
122.    
123. for (int r = 0; r < numReps; r++){
124.     range[r] = random(Ymargin + (NEWheight*(r*.202)), 
125.                                   NEWheight*(0.152+(r*.202)));
126.      }                          
127.                                   
128.       
129.                                   
130. for (int e = 0; e < numReps; e++){
131.       if (e <=2){
132.         end[e] = random( ((.9- (e*0.1) ) *width), width-Xmargin); 
133.       } else {
134.         end[e] = random( ((.9- ( (4-e) *0.1) ) *width), width-Xmargin); 
135.       }}
136. 
     
137. 
     
138. 
     
139. 
     
140. //accounting for margin change
141. 
     
142.  float newRange0 = (range[0])*margChange;
143.   float newRange1 = (range[1])*margChange;
144.   float newRange2 = (range[2])*margChange;
145.   float newRange3 = (range[3])*margChange;
146.   float newRange4 = (range[4])*margChange;
147. 
     
148. 
     
149. 
     
150. //major segments
151. 
     
152.   line (start[0], newRange0, end[0], newRange0);
153.   line (start[1], newRange1, end[1], newRange1);
154.   line (start[2], newRange2, end[2],  newRange2);
155.   line (start[3],  newRange3, end[3],  newRange3);
156.   line (start[4], newRange4, end[4], newRange4);
157.   
158.   
159.   
160.    
161. //minor segments  
162. 
     
163.   line (end[0], newRange0, end[1], newRange1);
164.   line (start[1], newRange1, start[2], newRange2);
165.   line (end[2], newRange2, end[3], newRange3);
166.   line (start[3], newRange3, start[4], newRange4);
167. 
     
168.  
169. }
170.