Knowledge Base

Import External Data Files with Missing Samples

Aim

To import external data files that contain gaps.

Prerequisites

• Your license for The Observer XT includes the External Data Module.
• The time series has a resolution of at least one decimal more than the resolution of the sample rate. So with a sample rate of 1 Hz, the time stamps are in seconds with at least one decimal.
• The file contains no entire empty rows.
• The file contains a column with time stamps.
• The file is exported as a text file.

Create an Import Profile for a Data Set with Missing Samples

1. Follow the general procedure in Create an Import Profile.
2. In the Import profile definition window, drop the column with the time information in the Time series cell. Do not use the Sample rate or Sample interval option.
3. If your data set contains missing samples indicated by non-numeric symbols, specify this symbol and select the Treat as number checkbox. Alternatively, click the button next to the Treat as number field to select one or more predefined symbols. To select a specific text, click <User Defined>, click OK and enter this text after a comma (,). If text is identified by a character, select this from the Text qualifier list.

Import a Data Set with Missing Samples

1. Follow the procedure in Import External Data as Text Files to import the dataset.
2. Choose the import profile you created for the dataset with missing samples. The following warning appears.
3. Choose Import and ignore and click OK.

Notes

• Missing samples may indicate that something is wrong with the setup of your DAQ system.
• The missing samples are converted into a NaN value, which are not present in the visualization and are ignored in the analysis.

Import Heartbeat Intervals

Introduction

Heartrate interval data by definition have a variable sample rate and do not meet the specification to import them as a text file. Heartbeat interval data can be imported as numerical modifiers. You can follow this procedure to import other data as well that do not meet the requirements to import them as external data.

Procedure

1. Open the heartbeat file in Excel.
2. Depending on the format of your Interbeat interval data file, either merge the time and millisecond columns, or create a time column and calculate the time stamps from the interbeat intervals. If not present already, add a column with the behavior IBI. Add a column with a sequence 1-2-1-2-1-2-1-2 etc.
3. Save the new file as a text file.
4. Close the text file before you proceed with the next steps.
5. In The Observer XT, open the observation in which you want to import the IBI file.
6. Click the Import data button on the toolbar, then select Import Observational Data.
7. Click Custom Import Profiles > Create New.
8. Click Browse and open the file with interbeat intervals that you have edited in Excel. The file appears in the Import Profile Definition window. Select Tab and Space under Select Data Delimiters and drag-and-drop the correct columns under Data Sets to the Time, Behavior, and Behavior Modifier columns. Do not drag the column with the actual interbeat interval data.
9. Click Save As, give the import profile a name and click OK and then Close.
10. In the Import Observational Data window, select the IBI file (*.txt) that you have edited in Excel.
11. Select State Events under Treat new Behaviors as, and make sure that the correct import profile is selected under Files of type. Click Open.
12. The new event log opens. Click the Offset button on the toolbar and choose Numerical offset.
13. Change the offset of the imported event log to 0:00:00.000 or the same time as the others. Click OK.
14. Open the visualization and check that all files are displayed (manual events, IBI and HRA).
15. If necessary, synchronize the imported data relative to the video. To do so, look at the video and find out when the physiological data recording device started recording. Adjust the time in the File Synchronization window.

Notes

• If HR recording started before starting video capture, the time shift for the IBI data is negative (e.g. if it started 10 seconds earlier, -0:00:10.000).
• If part of the data are not shown (for example, the first part of the IBI data that have been shifted before the start of the video), data were collected before you started video capture and may not be critical. However, if you want to show them from the very start, change the Start of the Observation in the Independent Variables window.

How IBI Data Are Shown

In the Coding Scheme

When you import the first IBI data file, the coding scheme shows a behavior IBI under a group named Behavior 1. The modifiers 1 and 2 are shown in the Modifiers view. They refer to the right-most column in the imported file. These modifiers are not used in analysis.

In the Visualization

The IBI are state events. The vertical bars inside the colored bar represent starts of the states (heart beats). The bar is single colored as the behavior is just one (IBI).

In the Statistics

To calculate statistics on the duration of IBIs:

1. Choose Analyze > Behavior Analysis > New > Calculate.
2. Click Layout and de-select Modifiers.
3. Double-click Behaviors and de-select the behaviors you are not interested in.
4. Click OK. Under the behavior IBI you find the corresponding statistics.

Source: The Observer XT 17 Help - External Data, Noldus Information Technology