processing phases/degrees confined within +-180degrees

a set data (1001 items of freuqency v 1001 items of degree) are output from Agilent PNA Network Analyzer.

it is then plotted with vertical axis being "degree", horizontal axis being "frequency"

it is observed the analyzer tends to confine the degrees within positive/negative 180 degrees. My estimate of the original data is the degrees keep decreasing constantly, but the analyzer tends to confines them within positive/negative 180 degrees.

how can i restore the constant drecreasing degrees with matlab? thx

[Azzi Abdelmalek]

what do you mean restore, from what? can you post a smple of your data and explain the problem?