Thank you Ulf for the reply.
Well i used this
for the the demonstration.
In this example, what i saw that x axis value is not fixed. Its getting changed as per value of minute given in data.
For example --
1. Use the sample program with nothing changed.
X axis --> 20:02, 20:04,20:06.......
2. commented these four value --
x axis value --> 21:01:00, 21:01:30, 21:02:00,....
And so on.
I am not getting, how to control these value?