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Calibration Model Wizard - Step 3 - Calibration & Validation data

Step 3 shows a first overview of all spectra and the calibration and validation data. Additional statistical analysis is also available:

The calibration data view in the upper part of the dialog shows an average spectrum (red line) derived from all data objects selected for calibration. The light red shape around the average spectrum indicates the variance of all spectra. If a particular data object is selected in the tree view below, the corresponding spectrum graph is shown as green line in the data view.

As in all data views in the software, the user can zoom into spectral regions by left clicking and dragging the mouse. A double-click in the data view restores the original view.

The experienced user will draw conclusions for selection of significant spectral regions. Some additional statistical spectra can be displayed as described below.

In the lower part of the dialog, a tree view shows all available data objects from the selected project. By default all objects are taken into account for calibration and none are used for validation. Corresponding property values of the selected property are shown accordingly.

The user can change the selection for calibration and validation spectra and also modify property values in this dialog.

Statistical spectra

Clicking the Statistical Spectra button shows a menu with several statistical spectra:

  • Show Correlation for property

  • Show Mean

  • Show Variance

  • Show Standard deviation

  • Show Calibration Spectra

  • Show Validation Spectra

  • Show Band

By checking or un-checking those entries the corresponding item is shown in the data view or not. The mean spectrum and the band are shown by default. The top of the menu will hold entries to show the correlation for each selected property.

Changing calibration and validation data selection

Data objects can be selected for use in calibration or validation data sets or both.

The selection of a single data object is modified by double clicking on Yes or No with the Left mouse button in the respective calibration or validation column field. In this case selection is toggled.

What is the minimum number of calibration spectra allowed?

For all calibration models except for the univariate model at least two spectra need to be part of the calibration set in order to perform a successful calibration.

For the univariate model one spectrum is sufficient, but additional options will be added to be able to perform a successful calibration: The flag Data Origin is Zero in the General Options of the Model Settings will be automatically activated and dummy spectrum with data value of (0,0) for all datapoints will be added to the calibration set and calibration project.

 

To change selection for multiple data objects at once, please select the project or folder node above in the tree. Then click the Right mouse button to show the following context menu. Alternatively multiple objects can be selected by holding the shift or ctrl button and left clicking.

  • Add to calibration set
    Adds all selected data objects to the calibration set. In the calibration column, all entries for those data objects will be changed to Yes.

  • Remove from calibration set
    Removes all selected data objects from the calibration set. In the calibration column, all entries for those data objects will be changed to No.

  • Add to validation set
    Adds all selected data objects to the validation set. In the validation column, all entries for those data objects will be changed to Yes.

  • Remove from validation set
    Removes all selected data objects from the validation set. In the validation column, all entries for those data objects will be changed to No.

Auto validation

Those users, who do not have a separate or independent set of validation spectra, may use the calibration spectra for validation purposes. In order to define a random set of validation spectra, click the Auto Validation button. The following dialog is shown:

  • Percentage of Spectra
    A user defined percentage of available data objects will be randomly assigned as validation spectra according to the following conditions:
  • Selection Based On
    • Calibration Data
      Only those objects in the tree being used in calibration (Calibration column entry = Yes) are considered for validation data selection
    • All Data
      All data suitable objects in the project are considered for validation data selection.

      Why are some data objects not considered?

      Only those spectra can be considered, which have a properly assigned component label. Especially for quantitative calibration modelling a numeric value must be present to be considered for use in calibration modelling.

  • Action
    • Toggle Selection
      This toggles the given percentage of the current active data selection. Spectra defined as calibration spectra become validation spectra and vice versa.
    • Only Activate Validation
      This keeps the current selection of calibration spectra and will only add the given percentage of validation data.

Cross Validation

Cross validation is another option to perform the validation of the calibration model. Please refer to the topic Cross Validation Setup in the chapter Chemometric Analyis for detailed description of the Cross Validation.

Modifying property values

Typically, all property values should be properly adjusted before starting the calibration wizard.

How can I edit the labels of my calibration data?

The most convenient way to add a new label, change existing label or remove labels from multiple spectra at once is using the Label Editor dialog. It can be started by clicking on the Edit Labels button on the right side of the window. Outside of the Calibration Model Wizard it can be started from the Tools menu.

 

Nevertheless, in some cases it will be necessary to change a property value during calibration, e.g. because of typing errors.

A value can be changed by clicking on it with the Left mouse button. In this case, the value becomes editable. After completion of changes, you need to click somewhere else to apply changes.

Navigation

Just click the Next > button to proceed to the next step.

Clicking the Cancel button will abort creating a new calibration.