@C_R All information you provided are greatly appreciated. I hope there will be less problems in my plotting with Maple.

@C_R  Yes, I agree. Thank you very much for showing us the details.

@C_R  what i did for the current purpose is to copy some useful mathML coding from this discussion platform, together with standard maple commands for plots. It works.

But for futute and long term consideration, knowing mathMLseems necessary for me. The bad thing is that i am a little bit old.

So far, i have not found any website that can translate a simple equation into mathML coding.

@C_R Thank you for the ideas. I will use mathML editor.

@tomleslie Thank you for showing me the use of units. I have one more question then. How do I change an italic font (part of letters) in an axis lable into a normal style, if I set lablefont=italic?

I find that if I type d (small), it shows in italic, if I type D (capital), it shows in normal style.

@mmcdara Thank you for your help. Is there any other way to get what I want, since I am not familiar with MathML?

@acer 

Dear acer: 

Since you know much more than many of us, may I ask you one more question?

When plotting a graph, can I place legend within the graph box, rather than above or below the box?

@acer This is really great!!

@tomleslie Thank you. It works.