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Rate of change
ROC expresses the percentage change from the price a selected number of bars earlier.
Lesson · Technical Indicators
Rate of Change and Momentum
Measure price change over a fixed lookback in percentage and absolute terms, compare zero-line crossings, adjust sensitivity, and distinguish momentum from trend direction and volatility.
Synthetic educational data
Core concepts
Understand what the indicator calculates, how its parameters affect it, and what it cannot establish by itself.
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Absolute momentum
Simple momentum subtracts the earlier price from the current price and retains price-unit scale.
3
Zero line
Positive values mean the current price is above the comparison price; negative values mean it is below. The crossing timing depends directly on lookback.
Interactive lesson
Change the inputs, inspect the calculation, and compare the indicator with the underlying price data.
PriceZero-cross markers
Rate of change12-bar comparison
Use a fixed-horizon momentum measure
Know exactly which prior price forms the comparison.
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Choose the lookback
Define how many completed bars separate current and comparison prices.
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Choose absolute or percentage form
Use momentum for price-unit change or ROC for normalized percentage change.
3
Interpret the zero line
Positive and negative values describe position relative to the lookback price.
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Define the event
Specify a zero cross, threshold, slope change, or divergence rather than using momentum as a vague adjective.
Fixed-horizon price change
Score 0 / 0Choose the best answer.
Lesson rule
ROC and momentum compare the current price with one specific past price; changing the lookback changes the question being answered.
Common mistakes
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Comparing raw momentum across price scalesA five-dollar move has different meaning for a $20 and a $500 instrument.
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Calling positive ROC a complete long setupIt only establishes that price is above its lookback reference.
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Changing lookback to force a desired zero crossParameter selection after seeing the outcome creates hindsight bias.
Completion standard
✓
Finish when you can name both prices in the calculation.
Identify current and lookback prices, calculate absolute and percentage change, explain the zero-line state, and compare signal timing under short and long lookbacks.
Calculation note: ROC uses percentage change from the exact price p bars earlier. Momentum uses simple subtraction. Corporate actions and adjusted versus unadjusted price data can materially affect historical calculations.