unity change rect transform size code example
Example 1: set width of rect transform unity
rectTransform.sizeDelta = new Vector2(50, 50);
Example 2: how to chnage the Scale propery of rect tranform unity
// To Change the "Scale" property use localScale, like this
// Change the numbers in the "()" to your choosen scale
public GameObject YourPanel;
YourPanel.GetComponent<RectTransform>().localScale = new Vector3(newWidthUI, newHeightUI, 1);
// If you want to change it in pixels
public GameObject yourUI;
yourUI.GetComponent<RectTransform>().sizeDelta = new Vector2(newWidthUI,newHeightUI);