how to draw spectrum diagram on android ?

I want to draw spectrum diagram but i cant ?

Are you going to tell us what you tried, or are we to assume that you tried to build an atomic bomb, and -once it went off- found that it didn't draw a spectrum diagram -whatever you mean by that- and so you came here to ask?

what i am trying to do is frequency meter to measure the GSM and WIFI frequency's and draw spectrum diagram