Stage 2 - Addition of Secondary Data
The purpose of this stage is to add a second set of data which will allow use to create an excel chart with 2 axis. This secondary data will not be displayed on the final chart and values should be selected well away from the primary data range.
In our example we have created a small table with values of -50 that is well away from the temperature range of the primary data.
The secondary data is added to the chart using the stages detailed above in the first section.
Highlight the chart and right click and choose Select Data this brings up the select Data source window which includes the primary temperature data.
Select "add" for a new data set to be added to the chart.
As this data will not be displayed only the Y values are required.
In our example the three -50 values are added to the chart.
Click the right button to return to the Edit Data series window then click on Ok as shown above.
This produces a chart that displays both the primary data and the additional secondary data, which will be hidden in the final stages.
Stage 3 - Creating a Primary and Secondary Axis Chart
This stage will separate the two sets of data on to two different axis. The secondary axis is the one which will be adjusted to align with the scale of the primary temperature scale.
Select the secondary data by clicking on any of the data points. When the data points are highlighted right click to bring up the data options and select Format Data Series as show above.
On the format data series select the first tab and click the Secondary Axis radar button as indicated above.
The two sets of temperature data are now displayed alongside each other but with different scales.