Descriptive Statistics

keywords: ALFA, summary statistics, descriptive statistics, groupwise

OUTLINE

1. Basic statistics
2. Summary statistics
3. Groupwise statistics

1. Basic statistics

You can find usual statistics such as mean, median and standard deviation of any of the arrays by just giving the command name and the array name. For example, you can compute mean of an array as

load tumor data
mean of id

Alfa will figure out what you are trying to do as long as the instructions are unambiguous

If you ask for the mean of non-numeric data, Alfa will fail to execute the command. All the statistics commands can be listed using list statistics commands.

2. Summary Statistics

Alfa also provides a summary command that computes the basic statistics of a data file. This can either take a bunch of arrays or the complete dataframe/dataset as an input. The summary command calculates the basic statistics for each of the variables provided and displays the result in a tabular format.

Example:

load tumor data
summary statistics of tumor data

Alternatively, you can also provide the following command:

summary statistics of area perimeter and texture of the tumor data

3. Groupwise Statistics

Groupwise statistics are useful to look at statistics of a variable based on a certain reference. For example, I want to look at the tumor area statistics for benign and malignant tumors, I can use groupwise statistics as follows:

load tumor data
set reference to tumor type [benign or malignant]
groupwise mean of area

This will give me a tabular result with mean area values corresponding to each tumor type.

Groupwise statistics can also be done to summarize the data.

Example:

load tumor data
set reference to tumor type [benign or malignant]
groupwise summary of tumor data