For the graph to represent your data most effectively, consider the following guidelines.
 For a matrix of plots, the data must include 2 to 20 columns of numeric or date/time data
 All columns must have the same number of rows. The data may also include up to three columns of categorical data for grouping.
 For a matrix plot of each Y versus each X, the data must include at least one column of numeric or date/time data for each X and each Y.
 All columns must have the same number of rows. The data may also include up to three columns of categorical data for grouping.
 The sample size should be medium to large
 You should consider the sample size for each scatterplot in the matrix plot. Although there are no formal guidelines for the amount of data needed for a scatterplot, larger samples more clearly indicate patterns in the data. A scatterplot that has a fitted regression line is most effective when the sample size is approximately 40 or greater. If the sample size is less than 40, the fitted regression line may not be as accurate.
 The sample data should be selected randomly
 In statistics, random samples are used to make generalizations, or inferences, about a population. If your data were not collected randomly, your results may not represent the population.
 Record data in the order it is collected

Usually, you should record the data in the worksheet in the same order that you collect it. Then, you can evaluate timerelated patterns in the data.