# How to choose asymmetric biplots in correspondence analysis

I have categorical data on Police Stations against Crime categories on a 2-way contingency table. I have an asymmetric row map and column map from correspondence analysis using XLSTAT. Which one of the two maps should be used to interpret the results?

Let me simply cite Help from SPSS Correspondence analysis

Normalization Method. Choose one of the following alternatives:

• Symmetrical. For each dimension, the row scores are the weighted average of the column scores divided by the matching singular value, and the column scores are the weighted average of row scores divided by the matching singular value. Use this method if you want to examine the differences or similarities between the categories of the two variables.

• Principal. The distances between row points and column points are approximations of the distances in the correspondence table according to the selected distance measure. Use this method if you want to examine differences between categories of either or both variables instead of differences between the two variables.

• Row principal. The distances between row points are approximations of the distances in the correspondence table according to the selected distance measure. The row scores are the weighted average of the column scores. Use this method if you want to examine differences or similarities between categories of the row variable.

• Column principal. The distances between column points are approximations of the distances in the correspondence table according to the selected distance measure. The column scores are the weighted average of the row scores. Use this method if you want to examine differences or similarities between categories of the column variable.

• Custom. You must specify a value between –1 and 1. A value of –1 corresponds to column principal. A value of 1 corresponds to row principal. A value of 0 corresponds to symmetrical. All other values spread the inertia over both the row and column scores to varying degrees. This method is useful for making tailor-made biplots.

With Principal method, you can obtain a plot only with row variable categories or only with column variable categories. With the other methods, you get biplot - both variables' categories are shown on the same plot. Symmetrical method is most often used.

I suppose that by asymmetric row map and column map you mean row and column principal biplots. There must be a way to request symmetric biplot.