Pie… charts enable you to compare the distributions of two sets of data. This is especially useful for comparing the distribution of a particular SOI phase against that of an entire 100 year simulation.

Pie charts rank the data in a simulation from the highest to the lowest value, and show the proportion of the data that lies in a particular range.

To use pie charts to compare two distributions:

1. Open the [Charts] menu and select [Pie…],
   …or click on the icon on the toolbar.
2. Select the data for analysis in the Pie form. Choose the simulation(s) you wish to analyse in the upper selection window, and the data you wish to analyse in the lower window.

There is a two-stage process for specifying the pair of simulations you wish to analyse using Pie… charts. The first dialogue box asks you to:

1. Select the simulation that will set the yield ranges for the wedges. It usually makes the most sense to select the all-years simulation here.
2. Select the number of pie slices you wish to view. For example, if you select three pie slices, Whopper Cropper ranks the data and divides it into terciles. This means that 33% of the data will lie in each pie slice.

3. Click <OK>.

A second selection screen asks which simulation you want to compare to the first one. Whopper Cropper takes the yield ranges from the first simulation, and ranks them within the second simulation to alter the relative size of the pie slices. Care is required to choose a simulation that is comparable to the first one selected. Usually it makes sense to choose one of the five SOI phases consistent with the all years simulation chosen on the first screen.

The size of the pie slices indicates the probability of crop yield falling within each range.

The example above indicates an increased probability of high yields, and a reduced probability of low yields, in years with a positive phase of the SOI compared to all 100 years of simulated yields.