Three Inside Up/Down (CDL3INSIDE)

Summary

A three-candle reversal pattern: a long real body, then a short real body totally engulfed by it (a harami), then a third candle of opposite color to the first that closes past the first candle's open. Signals a bullish reversal (three inside up, significant in a downtrend) or a bearish reversal (three inside down, significant in an uptrend).

Notes

Does not verify the prior trend the pattern classically assumes (three inside up is meaningful in a downtrend, three inside down in an uptrend).
Bulkowski's testing found Three Inside Up succeeds as a bullish reversal 65% of the time (rank 20 of 103 overall) and Three Inside Down succeeds as a bearish reversal 60% of the time (rank 56 of 103) — both meaningfully better than a coin flip. (thepatternsite.com)

Inputs

inOpen — Open price of each bar
inHigh — High price of each bar
inLow — Low price of each bar
inClose — Close price of each bar

Outputs

outInteger — +100 for three inside up (bullish reversal, first candle black), -100 for three inside down (bearish reversal, first candle white), 0 when no pattern. Computed as -candlecolor(1st)*100

Output Values

Value	Meaning
-100	Three Inside Down — bearish reversal, most meaningful after an uptrend
0	No pattern
100	Three Inside Up — bullish reversal, most meaningful after a downtrend

Properties

Numerical Stability: Start-Independent


☐ Overlap Input
✅ Independent Y-Axis i
✅ Candlestick i
☐ Can Output NaN or ±Inf
☐ Identity at Period 1

Implementation

TA-Lib Definition: cdl3inside.c · cdl3inside.yaml

Native	File
C	`ta_CDL3INSIDE.c`
Rust	`cdl3inside.rs`
Java	`Core_CDL3INSIDE.java`

TA-Lib is also available for Python, R and more using a wrapper.

Aliases

Three Inside Up/Down, Three Inside, Three Inside Up, Three Inside Down