The Advance-Decl Ratio indicator calculates the ratio of advancing issues to declining issues and plots this value. The relationship between advancing issues and declining issues is known as market breadth. For example, if a stock market index is rallying but there are more issues declining than advancing, then the rally is narrow and much of the stock market is not participating. To plot the Advance-Decline Ratio accurately, the chart must contain both the Advancing Issues and the Declining Issues and the inputs must specify the correct data number for each.
AdvIssues( Close of data1 ) sets the data series where Advancing Issues instrument is used
DecIssues( Close of data2 ) sets the data series where Declining Issues instrument is used