This calculates the average value for a series for each half calendar year within the display period. Half calendar years run from 1 January to 30 June and 1 July to 31 December.
CHA#(Expression,Carry Indicator,Display Indicator)
Where the optional Carry Indicator can be:
D Default; carry previous value, but not between periods
C Carry previous value
I Ignore
N N/A is displayed when there is a null value in the series
and Display Indicator can be:
P Values calculated for incomplete calendar periods at the start of the display period
R Values calculated for incomplete calendar periods at the start and end of the display
See Average format for details.
CHA#(FTSE100,C)
This calculates the average value of the FTSE 100 index for each half calendar year within the display period. Null values within the half-year are overwritten with the previous day's value. Values are carried over from half year.
The N parameter is not currently supported by the web Expression Builder in DFO / Datastream Charting, and the function is only accepted in the AFO Expression Builder if the Carry Indicator and the Display Indicator are included within the expression. The function is however fully supported when used directly in AFO or DFO requests, and a line will be plotted successfully in Datastream Charting.