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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 Methods

Hourly and daily mean values for recorded components are calculated by the IMOs, and are read from the archive file. There are several ways of calculating a full set of components for hourly and daily means from the minute means, you can choose from 3 slightly different methods. For a detailed description of these methods and their differences click here.

### Option 1: Calculate FDiff from minute means, and derive the remaining components

The mean FDiff is calculated from the minute means (the G values not including any that are FScalar), and then all other values are calculated from the three recorded component hourly and daily values and the calculated mean(FDiff).

### Option 2: Calculate FScalar from minute means, and derive the remaining components

The mean FScalar is calculated from the minute means (FScalar is derived for each minute mean by calculating FVector and taking the difference from FDiff), and then all other values are calculated from the three recorded component hourly and daily values and the calculated mean(FScalar).

### Option 3: Calculate the mean of all components from minute means

The mean of all components is calculated from the minute means. I need more help

## How to view the calculated values

Select 'Data Viewing Options', either from the 'Options' menu in the main tool bar. The top option gives you the different calculation methods. Click on the check box labelled 'Calculate missing hourly and daily means for FDiff and FScalar', and choose a calculation method from the radio buttons. Click OK at the bottom of the dialog. The next time you bring up a data viewing window the means will be calculated.

## How to compare calculation methods

Use the method above ("How to view the calculated values") to select a calculation method, and then select an observatory, and select 'view data'. On this data viewing window, select daily means. When these are displayed, leave the window open. Use the method ("How to view the calculated values") above again to change the calculation method. If you now select the same observatory, and 'view data', you will get another data window open, and you can select 'daily means' to view a new set of daily means. The two data windows which are now open will display results from the two different calculation methods you have chosen.

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