Abstract: An
example illustrating the ifexist() function
and the @v[] syntax
Product:
Statit
Custom QC
To check for the existence of a variable, you
can use the ifexist( ) function. The syntax
is:
ifexist("<Variable
name>")
The function returns 0 if the variable does
not exist. Otherwise it returns the variable
id number.
So in a command you might do something like:
if
ifexist("Temp") > 0 then let %cmd
= "let temp = temp * 2"
Now you have a command that is based on the
existence of a variable. How do you execute
it? This is where you would use the @v[ ] syntax.
This syntax allows you to drop the value of
a temporary variable in a Statit macro just
about anywhere, even as a command.
To execute this command you would:
let
%cmd = " "
if ifexist("Temp") > 0 then let
%cmd = "let temp = temp * 2"
@v[%cmd]
%cmd
is first set to a space. This is important because
the temporary variable %cmd will exsit as long
as the current session of Statit is running.
In Statit e-QC, this means that as long as you
are logged in this variable exists. In this
case, it may already exist when you run this
macro. You need to make sure you control what
is in it.
Next, if the condition is true, %cmd
would be set to contain the command "let
temp = temp * 2". If the condition
is false, it is left blank.
And the third line simply puts the contents
of %cmd on the next line of the macro. If it
is a space, nothing happens. If it contains
a command, the command is executed.
Here is another illustration of the use
of ifexist( ):
To store the variable ID number of the variable
Process_date in the temporary variable $var_id
let
$var_id = ifexist("Process_date")
Another illustration of the @v[ ] syntax:
Suppose your database stores an Upper Control
Limit (UCL) and a Lower Control Limit (LCL)
but sometimes they are returned as missing.
When they are there, you want them used in your
command. Perhaps they are returned from the
query in the variables UCL and LCL.
let
#ucl = UCL(1) ## Subscript in case the variable
has more than one case
let %ucl = " " ## Set to blank
if #ucl != #_sysmiss then %ucl = " /ucl
= #ucl " ## Load the string if the value
is not missing
let #lcl = LCL(1) ## Subscript in case the variable
has more than one case
let %lcl = " " ## Set to blank
if #lcl != #_sysmiss then %lcl = " /lcl
= $lcl " ## Load the string if the value
is not missing
##
Now you can use the two strings in a command.
gichart data by 2 @v[%ucl] @v[%lcl]
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