How to enlarge rect transform by script?

So I have text unity new ui object.

I want to enlarge this text's recttransform vertically so it can show more texts inside.

How can I do it at in-game dynamically?

I googled and used,

sysText.rectTransform.offsetMin, offsetMax,
RectTransformExtensions.SetRightTopPosition(sysRect, new Vector2(0, -OneLineHeight * many));

but neither works.

 

this is what i do - since it found it the most solid on mobile - but there is some other ways of doing it as well.

Code (CSharp):

1. RectTransform rt = this.GetComponent<RectTransform>();
2. rt.anchorMin = new Vector2( relativeX1, relativeY1 );
3. rt.anchorMax = new Vector2( relativeX2, relativeY2 );
4. rt.offsetMin = rt.offsetMax = Vector2.zero;

 

I never used unityUI, so was curious..
..is 2nd one: rt.anchorMax = new Vector2( relativeX2, relativeY2 );