There are several representations depending on the type of data under consideration. Six kinds of graphics are available depending on the selected data in the list of Y-Axis and X-Axis.
The spaghetti plot represents Y w.r.t. X by individual when both X and Y are continuous variable. This is one of the most used graphics. One can see for example a continuous observation with respect to time which is the first graphic of interest. In the warfarin example, one can plot the concentration w.r.t. time as in the following figure
The scatter plot represents dots of Y versus X when both X and Y are continuous variable and X is a covariate. In the warfarin example, one can plot the concentration w.r.t. the weight as in the following figure
Box & Whiskers Plot
The box blox represents the statistical representation of a continuous variable in box plot w.r.t. a discrete variable. It is a convenient way to graphically depict groups of numerical data through their quartiles. Box plots may also have lines extending vertically from the boxes (whiskers) indicating variability outside the upper and lower quartiles. In the warfarin example, one can plot the distribution of the weight w.r.t. the gender as in the following figure
It is very relevant to see the variation of an observation or a continuous covariate.
The cumulative histogram represents a cumulative count of a discrete variable w.r.t. a continuous variable. In the warfarin example, one can plot the cumulative count of the gender w.r.t. the weight as in the following figure
Histogram by group
The histogram plot represents a cumulative count of a discrete variable w.r.t. a discrete variable. In the warfarin example, one can plot the cumulative count of the gender w.r.t. the age as in the following figure
(Kaplan-Meier estimator and events mean)
Links between graphics and combinations of variables
Here is a summary table that shows which plot is used for each combination of X and Y data.
|Continuous observation||Continuous observation||Spaghetti|
|Continuous observation||Continuous covariate||Scatter|
|Continuous observation||Discrete covariate||Box plot|
|Discrete observation||Time||Cumulative histo|
|Discrete observation||Regression||Cumulative histo|
|Discrete observation||Continuous covariate||Cumulative histo|
|Discrete observation||Discrete covariate||Histo. by group|
|Continuous covariate||Continuous covariate||Scatter|
|Continuous covariate||Discrete covariate||Box plot|
|Discrete covariate||Continuous covariate||Cumulative histo.|
|Discrete covariate||Discrete covariate||Histo. by group|