# Spectrum Analysis

There are many phenomena including big waves and small waves.

##
For Periodical Data

Fourier Transformation
is used to analysis periodic phenomena.

Periodicity is showed as frequency.
This analysis is called "Frequency analysis" or "Spectrum analysis"

##
For Non-Periodical Data

Even if the data is not periodic, approximation of periodic data is effective.

Data has range of numbers.
Using the range as the maximum periodicity, we can use the method of periodic data.

##
Analysis of Time and Space

If there are big waves and small waves along time series,
spectrum analysis is used as
Time Series Analysis
.

This method is also used for spatial analysis of big waves and small waves.

##
Filter

The data of waves contains various frequencies.
If we need to study specific frequency, other frequencies are
noise
.

"Low pass filter" used to analyze high low frequency like warp or crookedness. It eliminates high frequency.

"High pass filter" used to analyze high low frequency like roughness. It eliminates low frequency.

NEXT Treatment of Time