
A variable is a location in your computer’s memory that has a name and where you can store something, as explained in §3.2 and §3.4. In a Praat script, you can store numbers and texts, i.e. you can use numeric variables and string variables.
Numeric variables can hold integer numbers between 1,000,000,000,000,000 and +1,000,000,000,000,000 or real numbers between 10^{308} and +10^{308}. The smallest numbers lie near 10^{308} and +10^{308}.
You use numeric variables in your script like this:
length = 10
Draw line: 0, length, 1, 1
This draws a line in the Picture window from position (0, 10) to position (1, 1). In the first line, you assign the value 10 to the variable called length
, and in the second line you use the value of length
as the second argument to the command Draw line....
Names of numeric variables must start with a lowercase letter, optionally followed by a sequence of letters, digits, and underscores.
You use string variables, which contain text, as follows:
title$ = “Dutch nasal place assimilation”
Text top: “yes”, title$
This writes the text "Dutch nasal place assimilation" above your drawing.
As in the programming language Basic, the names of string variables end in a dollar sign.
You can write the content of numeric variables directly to the info window:
x = 2.0
root = sqrt (x)
writeInfoLine: "The square root of ", x, " is ", root, "."
This will write the following text to the Info window:
The square root of 2 is 1.4142135623730951.
You can fix the number of digits after the decimal point by use of the fixed$
function:
x = 2.0
root = sqrt (x)
writeInfoLine: "The square root of ", fixed$ (x, 3), " is approximately ", fixed$ (root, 3), "."
This will write the following text to the Info window:
The square root of 2.000 is approximately 1.414.
By using 0 decimal digits, you round to whole values:
root = sqrt (2)
writeInfoLine: "The square root of 2 is very approximately ", fixed$ (root, 0), "."
This will write the following text to the Info window:
The square root of 2 is very approximately 1.
By using the percent$
function, you give the result in a percent format:
jitter = 0.0156789
writeInfoLine: "The jitter is ", percent$ (jitter, 3), "."
This will write the following text to the Info window:
The jitter is 1.568%.
The number 0, however, will always be written as 0, and for small numbers the number of significant digits will never be less than 1:
jitter = 0.000000156789
writeInfoLine: "The jitter is ", percent$ (jitter, 3), "."
This will write the following text to the Info window:
The jitter is 0.00002%.
All of the variables you saw earlier in this tutorial were defined at the first moment a value was assigned to them. Some variables, however, are already defined implicitly at the start of your script.
Some predefined numeric variables are macintosh
, windows
, and unix
, which are 1 if the script is running on a Macintosh, Windows, or Unix platform (respectively), and which are otherwise zero. Another one is praatVersion
, which is e.g. 6400 for the current version of Praat.
Some predefined string variables are newline$
, tab$
, and shellDirectory$
. The last one specifies the folder that was the default folder when Praat started up; you can use it in scripts that run from the Unix or Windows command line. Likewise, there exist the predefined string variables homeDirectory$
, preferencesDirectory$
, and temporaryDirectory$
. These three refer to your home folder (which is where you log in), the Praat preferences folder, and a folder for saving temporary files; if you want to know what they are on your computer, try to write them into a script window. The variable defaultDirectory$
is available for formulas in scripts; it is the folder that contains the script file. Finally, we have praatVersion$
, which is “6.4” for the current version of Praat.
To check whether a variable exists, you can use the function
variableExists (variableName$)
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