One can easily change RectTransform right,left,top and bottom value using script in this way :-

object.GetComponent<RectTransform> ().offsetMin = new Vector2 (0,-1);//left-bottom

here "0" indicates Left value and "-1" indicates bottom value.

Similarly for setting Right and Top value use:

object.GetComponent<RectTransform> ().offsetMax = new Vector2 (0,1);//right-top

here "0" indicating Right value and "1" indicating Top value.

In my case value is 0 or 1. But it can be any value rather than 0 or 1.

e.g:-

object.GetComponent<RectTransform> ().offsetMin = new Vector2 (10,12);//left-bottom
object.GetComponent<RectTransform> ().offsetMax = new Vector2 (20,40);//right-top

For more understanding :-

• rectTransform.offsetMin.x        // Left
• rectTransform.offsetMin.y       // Bottom
• rectTransform.OffsetMax.x    // Right
• rectTransform.offestMax.y    // Top

Hopefully this will be helpful for you.

Thanks!