Pointers on Data Desk Version 4

This is a brief summary of some basics of Data Desk - See the fine book
Learning Data Analysis with DATA DESK
by Paul Velleman for much more complete descriptions.

Data Desk is an easy to use statistics program for Macintoshes whose user interface very much follows the ``desktop'' paradigm present on Mac and Windows machines. In fact when you open Data Desk, it puts its own version of the desktop on top of the Mac's usual one.

Each Variable appears as an icon which you can doubleclick on to inspect the numbers. The different rows visible when you open such an icon correspond to the different cases, (individuals) in the relation. You can think of a relation as being a table with one column for each variable, and one row for each case. The entry in the corresponding spot of the relation is the value of the variable for that individual. Different variables in the same relation will generally be in the same folder.

Operation on data in Data Desk is largely through menus and selection. Typically to use a menu entry, you need to first select appropriate variables that the command is to work on. (For example the variables being plotted ...) Because some operations involve processes that are not symmetric in their arguments (e.g. you might want one specific variable on the horizontal axis), there are notions both of selecting a variable as ``X'' and as ``Y''. Until you select the right arguments, menu entries will frequently be grayed out. Details are described below in the section on selection.

Topics covered below include:

Selecting Icons

X Variables
may be selected by holding shift down while clicking on the icon.
Y Variables
may be selected by holding option down while clicking on the icon.
Multiple Selection
may be accomplished by dragging a rectangle around the icons of interest.
one icon from a collection may be done by holding both shift and option down while clicking on the icon.


Computation is generally selected from the Calc menu.

Each computation typically gives a new icon (which can be doubleclicked to open) in the results folder.

The Summaries
submenu of Calc can be used to generate Reports after the desired summary statistics are chosen. Reports are where you will find means, standard deviations, ranges, quantiles, and many other statistics of interest.
Select Summary Statistics
from Calculation Options under the Calc menu offers many choices about what to report for each selected variable.
Derived Variables
can also be used for many calculational purposes. More details below.
is available under the Calc menu and Regression Options is on the Calculation Options submenu.
Confidence Intervals
are available by choosing Estimate... from the Calc menu.
Significance (Hypothesis) Testing
is available by choosing Test... from the Calc menu.


Generating plots generally involves selecting suitable icons (often as x's or y's) and then choosing a suitable plot command.

Plots may be moved by dragging with the mouse.

Bar Charts
count the number of cases in a a (usually) non-numeric variable.
are produced by the same method as dotplots but add information such as the 25th and 75th percentiles, outliers, and the median.
involve selecting numeric data as y and categorical data as x.
display numeric data in bars. Bar width can be adjusted by choosing Plot Scale from the hyperview menu (sidewise triangle) to the left of the title of the histogram window. to the number of cases
require the selection of one numeric variable and plot this against the case number (which starts at 1.)
Normal Prob Plots
plots the actual sorted values of the selected variable against a hypothetical normal distribution determined by the NScores function.
like barcharts count up the number of cases.
Rotating Plots
require the selection of 3 numeric variables. They may be set into continued motion by releasing the mouse while dragging.
reuire the selection of numeric x and y variables. The hyperview menu includes the possibility of adding a least squares line of regression.

Editing and Entering Data

Data is entered into a new or existing variable.

of a new variable is by means of choosing Blank Variable from the submenu New of the menu Data.
can be either horizontal or vertical. A vertical cursor is for editing one entry in a variable. A horizontal cursor is for inserting a new case.
Selection of Cases
for copying or cutting a range of cases is accomplished by dragging horizontally or vertically.
Pressing Command while Clicking the Mouse
allows one to add an additional case to those already selected.
advances to the next case (depending on preferences.) With a horizontal cursor, it does not automatically create an empty new case below. Just start typing if you want to create that new case.
advances to the next variable in the case if the sequence box (at the top of the right scroll bar for the variable) is active.

Generating Data

This is possible using commands from the Manip Menu.

If you are just starting Data Desk and wish to start out by generating random or patterned data, an easy way to do this is to select enter data from keyboard, and then cancel from the dialog naming the new variable.

Generate Patterned Data
This command can be used to generate a sequence of case numbers (e.g. 1,2, ..., n), or other linearly spaced data.
Generate Random Numbers
Possibilities include distributions (uniform, normal, and Poisson), Bernoulli trials (sequences of 0's and 1's), and binomial experiments representing cumulative results of Bernoulli trials. In the dialog box here, the number of cases will be the number of rows (values) in each variable. By changing the number of variables requested from its typical default of 1, you can simultaneously do several simulations.


Layouts are one of the best ways to assemble results for printing. Images of other windows are moved into layouts by copying and pasting. Alternatively one can drag icons. Images can then be dragged around and resized within the layout to achieve the desired effect.

of layouts is by means of choosing Layout from the submenu New of the menu Data.
is entered into a layout by typing it into a scratchpad and then either
  1. selecting the text and using copy and paste or,
  2. by dragging its icon into the layout.
Font size for the text can be selected from the hyperview menu (triangle to the left of the title) of the scratchpad.


can be used to collect graphics, explanations, and computation results on one piece of paper.
Save Desktop Picture
will produce 2 sheets of paper on a 14 inch monitor and 4 sheets of paper on a 15 inch monitor unless you resize or rotate the image. Selecting landscape (the picture turned sideways) from the Page Setup dialog box will rotate by 90 degrees and better use a sheet of paper.


for layouts is best entered in a scratchpad, selected, copied, and then pasted into the layout.
can be performed in a scratchpad by entering any expression legal in a derived variable, selecting it, and then either pressing command-= or choosing Evaluate Derived Variable from the Manip menu. (So arithmetic expressions not involving variables are allowed here.)

Importing and Exporting Data

These commands can be used if you want to first enter your data in a text file, or if you'd like to use a spreadsheet for part of your analysis.
from the file menu produces by default a new ASCII tab delimited file. Before choosing export, select the variables you wish to export in the order you wish them to appear in the new file.
creates a new relation from such a tab-delimited file. Variables may be dragged from one relation to another as long as both relations have the same number of cases.


Display and Hiding
can be accomplished by choosing Palettes from the Manip menu.
The Paintbrush and Lasso tools
can be used to conveniently select cases from a plot. By holding the shift key down, the cases you click on are added to previous selections rather than replacing them.
The Question Mark tool
can be used on a plot to find out the variable value which goes with the data point. For this to work, the variable window with the data you want to see when you click should be open, and the last variable selected.

Sorting and Ranking Data

Sorting and Ranking commands are found under the Manip menu.

produces a new variable for each selected variable. The new variable records the position of each case in sorted order of the variable.
Sort on Y, Carry X's
creates a new relation in which the cases have been reordered by values of the variable chosen as y. All x variables selected are also copied and reordered in the new relation. A new variable holding the original case index of each new row also appears.
Sorting and Ranking Options
appear below Manipulation Options in the Manip menu.

Text Font Size

Bigger Font Sizes
may be selected from the hyperview menu - a triangle just to the left of the window title.

Derived Variables

These are either created from the Transform menu of Calc or from New of the Data menu.

Although menu based choices of selected icons may be used, derived variables are recorded textually. Doubleclicking on a derived variable created by a menu command will illustrate how the language of derived variables works.

expressions like '(5*X[i] - 3*Y[i])/Mean(X)' are allowed.
If ... Then ... Else ...
is possible and illustrated in the string example below.
Sample Derived Variable
data can be generated using double quotiation marks, e.g.
		if assets > 10000 then
		else if assets > 2000 then
A string Variable_Name
(possibly within backquotes) may be used in a derived variable to refer to another. The value of this expression for each case will be the value of that case in the variable named by Variable_Name.
refers to the i'th case of the variable named by Variable_Name.

Using Selectors

Working on a Portion of Your Data
may be accomplished by the following procedure:
  • First select the cases you want to use. The lasso from the Tools menu under Modify is a convenient way to do this graphically.
  • Choose Assign Selector from the Selection submenu of the Modify menu. This creates a new variable whose value on the cases you selected earlier is 1 and 0 otherwise. A corresponding button is also created.
  • When you turn this button on (black color), many subsequent operations in DataDesk will only use the cases where this variable takes the value 1; i.e. the cases you selected.


Grouping data based on the value of a categorical variable
may be accomplished by the following procedure:
  • Select the categorical variable as x.
  • Select the other variables you wish to break up as y's.
  • Now choose Split into Variables by Groups from the Manip menu. This will create subfolders, one subfolder for each value of the categorical variable. Within each subfolder will be the carried along y values for the cases whose categorical variable takes the value corresponding to that subfolder.


are created from the New submenu of the Data menu.
have their ranges adjusted by the Plot Scale entry of the hyperview menu.
are used as a derived variable would be by referring to the name of the slider.
Last Update: August 24, 2000