# True Strength Index

The True Strength Index (TSI) is a momentum-based indicator developed by William Blau. The TSI is suitable for intraday time frames as well as long term trading and helps to define trend and oversold/overbought conditions.

The formula for TSI is:

TSI = ExpMovAvg(ExpMovAvg(NetChange, Long),Short) / ExpMovAvg(ExpMovAvg(AbsNetChange(n), Long),Short)

Long = Long Period

Short = Short Period

NetChange = Price - Price 1 bar ago

AbsNetChange = Absolute value of Price - Price 1 bar ago

`XAVG(XAVG(C - C1, s), l) / XAVG(XAVG(ABS(C - C1), s), l)` |
`s` =ShortPeriod, `l` =LongPeriod |

Where `s`

is the short period which must be an integer.

Where `l`

is the long period which must be an integer.

### Examples

A True Strength Index 3, 9 can be written as follows.

`XAVG(XAVG(C - C1, 3), 9) / XAVG(XAVG(ABS(C - C1), 3), 9)`