Generating Date/Time Data

PV-WAVE Foundation > User Guide > Working with Date/Time Data > Generating Date/Time Data

You can generate date/time data for data files that do not have date and time stamps. There are two steps:

Create an initial date/time structure using one of four conversion functions: STR_TO_DT, VAR_TO_DT, SEC_TO_DT, or JUL_TO_DT.

Use the DTGEN function to create a variable from the original function that contains an array of date/time structures.

The DTGEN function has the basic form:

result = DTGEN(dt_start, dimension)

Example 1

Assume that you have a file that contains seismic data collected on an hourly basis for the month of April, 1992. The file contains the seismic data, but does not have a time stamp appearing with each data entry. The file looks like:

Seismic data

1.03

2.04

1.33

4.45

The first data entry (1.03) was taken at 1:00 a.m on April 1, 1992. Each successive entry was taken on an hourly basis for the rest of the month. To generate date/time data for all of the hours of the month:

; Use VAR_TO_DT to create the initial date/time variable for

; April 1, 1992, 1:00 a.m.

date1 = VAR_TO_DT(92,4,1,1)

PRINT, date1

; PV-WAVE prints: { 1992 4 1 1 0 0.00000 87493.042 0}

; Generate a date/time array variable that contains a date/time

; structure for every hour in the month of April

; (24 hours * 30 days =720 hrs).

dtarray = DTGEN(date1, 720, /hour)

PRINT, dtarray

; PV-WAVE prints the following:

; { 1992 4 1 1 0 0.00000 87493.042 0}

; { 1992 4 1 2 0 0.00000 87493.083 0}

; { 1992 4 1 3 0 0.00000 87493.125 0}

; .

; .

; { 1992 5 1 0 0 0.00000 87523.000 0}

Example 2

You can also use the Compress keyword with the DTGEN function. This example creates a date/time variable that contains all of the weekdays for the month of January.

; Creates an initial date/time variable to use with the DTGEN

; function.

date1 = VAR_TO_DT(1992,1,1)

; Defines the weekend days.

CREATE_WEEKENDS, ['sat', 'sun']

; Generates a date/time variable that contains the weekdays for

; January. The Compress keyword excludes the weekend days.

dates = DTGEN(date1, 23, /Compress)

DT_PRINT, dates

; PV-WAVE prints the following:

; 01/01/1992

; 01/02/1992

; 01/03/1992

; 01/06/1992

; 01/07/1992

;      .

;      .

Notice that the 4th and 5th of January have been removed (compressed) from the result. These days fall on Saturday and Sunday.