Schaff Trend Cycle (STC)

Summary

Schaff Trend Cycle (Doug Schaff): a MACD line passed twice through a stochastic, each pass smoothed by half. Bounded 0 to 100, read against 25 and 75: turning up from below 25 is bullish, turning down from above 75 bearish.

Chart

Reference data (CSV) · Chart (SVG)

Chart metadata i

Outputs

• outReal: line · zero · positive · levels: 25, 75

Formula

MACD[t] = EMA(x, fast)[t] - EMA(x, slow)[t]

Frac1[t] = 100 * (MACD[t] - min(MACD, cycle)) / (max(MACD, cycle) - min(MACD, cycle))

PF[t] = PF[t-1] + 0.5 * (Frac1[t] - PF[t-1])

Frac2[t] = 100 * (PF[t] - min(PF, cycle)) / (max(PF, cycle) - min(PF, cycle))

STC[t] = PFF[t] = PFF[t-1] + 0.5 * (Frac2[t] - PFF[t-1])

min and max are taken over the last cycle values, current one included. When a range is zero, the fraction keeps its previous value (0 before any). Each smoother starts on its first input.

Notes

• The smoothing factor is fixed at 0.5, as in Schaff's published code.
• The MACD line is TA-Lib's: both EMAs are seeded with a simple average over windows ending on the same bar. The published code runs the EMAs from the first bar of the data.
• If the slow period is set smaller than the fast period, the two are swapped, as in MACD.
• Being recursive, an output depends on how much history precedes it. The unstable period warms the two smoothers; the EMA unstable period warms the MACD line.

Inputs

• inReal — Input series (typically close)

Outputs

• outReal — Schaff Trend Cycle, from 0 to 100

Parameters

Parameter	Type	Default	Accepted values	Description
optInFastPeriod	integer	23	2–100000	Period of the fast EMA
optInSlowPeriod	integer	50	2–100000	Period of the slow EMA
optInCyclePeriod	integer	10	2–100000	Window of both stochastic stages

Properties

Numerical Stability: Initial Unstable Period — Tunable via STC's own unstable period and EMA's, which STC computes internally.

☐ Overlap Input
✅ Independent Y-Axis i
☐ Candlestick
☐ Display Shift

☐ Can Output NaN or ±Inf
☐ Identity at Period 1
☐ Uses Transcendental
☐ Input Must Be Positive

Example

C

#include <stdio.h>
#include <ta_libc.h>

int n = 252;
double series[252]; /* your data, oldest first */
double out[252];
int outBegIdx, outNBElement;

TA_Initialize();
TA_STC( 0, n - 1, series, 23, 50, 10, &outBegIdx, &outNBElement, out );
printf( "%d values from bar %d; last out = %f\n", outNBElement, outBegIdx, out[outNBElement - 1] );

Rust

use ta_lib::Core;

let series = vec![0.0; 252]; // your data, oldest first
let mut out = vec![0.0; 252];

let core = Core::new();
let range = core.stc(0, series.len() - 1, &series, 23, 50, 10, &mut out)?;
println!("{} values from bar {}; last out = {}", range.count, range.beg_idx, out[range.count - 1]);

Java

import io.github.talib.Core;
import io.github.talib.OutRange;

double[] series = new double[252]; // your data, oldest first
double[] out = new double[252];

Core core = Core.DEFAULT;
OutRange r = core.stc(0, series.length - 1, series, 23, 50, 10, out);
System.out.println(r.count() + " values from bar " + r.begIdx() + "; last out = " + out[r.count() - 1]);

C#

using System;
using TALib;

var series = new double[252]; // your data, oldest first
var outReal = new double[252];

var core = Core.Default;
OutRange r = core.Stc(0, series.Length - 1, series, 23, 50, 10, outReal);
Console.WriteLine($"{r.Count} values from bar {r.BegIdx}; last outReal = {outReal[r.Count - 1]}");

TypeScript

import { stc } from 'ta-lib';

const series = new Float64Array(252); // your data, oldest first

const { begIdx, values } = stc(series, {
  fastPeriod: 23,
  slowPeriod: 50,
  cyclePeriod: 10,
});
console.log(values.length + ' values from bar ' + begIdx + '; last values = ' + values[values.length - 1]);

Implementation

Added in 0.8.3 (ta-lib-python 0.8.3).

TA-Lib Definition: stc.c · stc.yaml

Native	File
C	ta_STC.c
Rust	stc.rs
Java	Core_STC.java
C#	Core_STC.cs
TypeScript	stc.ts

Python: talib.STC (ta-lib-python 0.8.3 or later), see ta-lib-python.

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

Aliases

Schaff Trend Cycle, Schaff TC

See Also

MACD · STOCHF · STOCHRSI

References

• Doug Schaff, "Releasing the Code to the Schaff Trend Cycle", FX-Strategy.com, published on FXStreet.com, February 15, 2008. The EasyLanguage source, and the 23/50/10 defaults.
• Doug Schaff, "Catching Currency Moves with The Schaff Trend Cycle Indicator", Chartpoint, July/August 2002.