This section contains examples using data feed scripts to read data, set up a live control chart, and store scripts in a data table.
Here is a typical data feed script. It expects to find a string 3 characters long starting in column 11. If it does, it uses it as a number and then adds a row to the data table in the column “thickness.”
feed = Open Datafeed( );
myScript = Expr(
line = feed << Get Line;
If( Length( line ) >= 14,
x = Num( Substr( line, 11, 3 ) );
If( !Is Missing( x ),
dt << Add Row( {thickness = x} )
);
);
);
Assign the script to the data feed object by using Set Script:
feed << Set Script( myScript );
Here is a sample script that sets up a new data table and starts a control chart based on the data feed.
dt = New Table( "Gap Width" ); // make a data table with one column
dc = dt << New Column( "gap", Numeric, Best );
// set up control chart properties
dc << Set Property(
"Control Limits",
{XBar( Avg( 20 ), LCL( 19.8 ), UCL( 20.2 ) )}
);
dc << Set Property( "Sigma", 0.1 );
// make the data feed
feed = Open Datafeed();
feedScript = Expr(
line = feed << Get Line;
z = Num( line );
Show( line, z ); // if logging or debugging
If( !Is Missing( z ),
dt << Add Row( {:gap = z} )
);
);
feed << Set Script( feedScript );
// start the control chart
Control Chart Builder(
Show Capability( 0 ),
Variables( Y( :gap ) ),
Set Subgroup Size( 5 )
);
/* Either start the feed from the device or test-feed some data
to see it work (comment out one of the lines):
feed << Connect( Port( "com1:" ), Baud( 9600 ) );*/
For( i = 1, i <= 20, i++,
feed << Queue Line( Char( 20 + Random Uniform() * .1 ) );
Wait( .1 ); // simulate a delay in the feed
);
You can further automate the production setting by placing a data feed script such as the one above in an On Open data table property. A property with this name is run automatically each time the table is opened (unless you set a preference to suppress execution). If you save such a data table as a template, opening the template runs the data feed script and creates a new data table.