How tro calculate wavelenght/frequency

[pekkaj]

Hi
I'm writing code with c++ for PS2000 driver:
ps2000_set_channel
ps2000_set_trigger
ps2000_get_timebase
ps2000_run_block
ps2000_ready
ps2000_get_times_and_values
So I have after that:
time_interval
time_units
number_of_values_read
peak_count
time_indisposed_ms
buffer_size_bytes
I can draw nice sine curves by read values but how to calculate wavelenght/frequency?
Pekka