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# Intermagnet CD Data Viewer Help

# Calculation of Hourly and Daily Mean FDiff Values

IAF2.0 file format specifies that the F Difference values for hourly and daily means should be marked as missing. If you wish you can select the option for these to be calculated by the CD Data Viewer. This does take a noticable amount of time in the case of the annual means plot, causing a delay of 2 or 3 seconds.

## Calculation Method

FDiff hourly mean will be the mean of all the G values from each minute mean for that hour.

FDiff daily mean will be the mean of all the G values from each minute mean for that day.

Hourly and daily mean values for recorded components are provided by the IMOs, and are read from the archive file. All other calculated components (including FScalar - the total field value) are derived from this vector of mean values, and not from the minute means.

## How to view the calculated values

Select 'Plot Options', either from the 'Options' menu in the main tool bar, or use the 'Plot Options' button at the base of a data plot.

Click on the 'Calculate Mean FDiff' radio button to enable the calculation. FDiff will now be calculated for every plot until it is switched off using this same 'Plot Options' dialog.

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