3.7.5.5 Curve

Curve-obj

LabTalk Object Type:

External Object

The curve object provides for the following math operations on a data plot:

• Smoothing
• Integration
• Derivation

It also provides for baseline operations and peak selection.

See the common properties and methods of external objects.

Please see the addtool_curve_integ X-Function.

Properties:

Common Curve Object Properties

Curve Object Properties Specific to Math Operations

Curve Object Properties Specific to Baseline Operations and Peak Selection

Methods:

Curve Object Methods Specific to Math Operations

Curve Object Methods Specific to Baseline Operations and Peak Selection

Examples:

Differentiation Using Savitzky-Golay Method

This script performs a differentiation using the Savitzky-Golay method:

 
//Create a new book and import the data
newbook;
string fpath$ = "Samples\Signal Processing\fftfilter1.dat";
string fname$ = system.path.program$ + fpath$;
impasc;
wks.addcol();
col(c)[L]$=Results;
//Assign datasets
curve.data$=%H_B;
curve.result$=%H_C;
curve.i1 = -1;
curve.smoothpts = 5;
curve.derivdeg = 1;
//Perform differentiation, 
//fill Result column of original worksheet
curve.sgderiv();

Peak Integration from a Baseline

This script performs an integration from a baseline:

//Open a new worksheet
newbook;
//Import sample file;
string fpath$ = "Samples\Spectroscopy\Peaks with Base.DAT";
string fname$ = system.path.program$ + fpath$;
impasc;
//Create a column for results
wks.addcol();
col(D)[L]$=Results;
curve.data$ = %H_B;
curve.base$ = %H_C;
curve.result$ = %H_D;
//Perform integration, 
//fill results column of original worksheet
curve.integrate();
//Send the total area to the script window
type "Area = $(curve.integrate.area)";

Example 3
This script finds peaks in the active data plot and adds the peak XY values and row index numbers to the original worksheet:

 
curve.reset();  //initialize
%W = %[%C,'_']; //get name of wks for active data in layer
%W!page.xlcolname = 0; //turn off Spreadsheet Cell Notation firstly;
%W!wks.addcol(Pkindex); //add column to store index value
%W!wks.addcol(Pkx);  //add column to store x value
%W!wks.col$(%W!wks.ncols).type = 4;  //set as X column
%W!wks.addcol(Pky);  //add column to store y value
curve.data$ = %C;  //dataset to find peak values
curve.peakIndex$ = %W_PkIndex;
curve.pickPeaks.rectHeight = .05;
curve.pickPeaks.rectWidth = .05;
curve.pickPeaks.minHeight = .05;
curve.pickPeaks(1);  //pick peaks without a definable baseline
get %W_PkIndex -e end;
for (ii = 1; ii <= end; ii += 1)
{
      %B = curve.data$;  // %B is current active dataset
      index = %W_pkindex[ii]; // get peak index
      %W_Pkx[ii] = xvalue(index,%B); // Set corresponding x value 
      %W_Pky[ii] = %B[index];  // Set corresponding y value
}

For the Spreadsheet Cell Notation in the workbook, please see FAQ-849 for more information.

Example 4
This example use curve.smoothLeftPts and curve.smoothRightPts to set the smoothing points.

//Create a new book and import the data
newbook;
string fpath$ = "Samples\Signal Processing\fftfilter1.dat";
string fname$ = system.path.program$ + fpath$;
impasc;
wks.addcol();
wks.addcol();

//smoothing points = 10
col(c)[c]$=10-point;
curve.data$=%h_B;
curve.result$=%h_c;
curve.smoothleftpts=2;
curve.smoothrightpts=3;
curve.smoothpts=curve.smoothleftpts + curve.smoothrightpts + 1; 
curve.polyDeg = 2;
curve.derivdeg = 1;
curve.sgderiv();