asDate#

Purpose#

Converts columns of matrices, string arrays or dataframes to dates, with the option to specify the display format.

Format#

x_date = asDate(X[, fmt, columns])#

Parameters:

X (NxK matrix, string array or dataframe) –
data.

If X is a string array, the following formats are accepted:
```
YYYY-MM-DD HH:MI:SS
YYYY-MM-DD HH:MI
YYYY-MM-DD HH
YYYY-MM-DD
YYYY-MM
YYYY
```
fmt (Mx1 string array) – Optional input, contains strftime date/time format characters.
columns (Mx1 scalar or string) – Optional input, the names or indices of the date columns in X to set format of.

Returns:

x_date (NxK dataframe) – contains metadata assigning the date display format specified by fmt to the variables in x specified by columns.

Examples#

Example 1: Convert strings to dates with the default format#

asDate() will automatically interpret date strings formatted like this, 2018-02-14 06:31:27. Only the four digit year is required. Any portion of the remaining information may be present as long as all preceding information is also present.

The display format will be set to reflect the input string. For example:

print asDate("2018-02-14");

        X1
2018-02-14

// Create two dates with the same date,
// but different display formats
dt_1 = asDate("2018-02");
dt_2 = asDate("2018-02-01");

print "dt_1 = " dt_1;
print "dt_2 = " dt_2;
print "dt_1 == dt_1"; (dt_1 == dt_2);

will print the following.

dt_1 =
              X1
         2018-02

dt_2 =
              X1
      2018-02-01

dt_1 == dt_1
       1.0000000

// Create a 2x1 string with dates
// of different precision
dt_str = "2003-06-17" $| "2003-06-18 09:21:30";

// Convert to a dataframe
dt_df = asDate(dt_str);
print dt_df;

The above code will print out:

              X1
2003-06-17 00:00
2003-06-18 09:21

Example 2: Convert date strings with arbitrary formats#

The second, optional, input allows you to specify any arbitrary format using the format specifiers listed in the command reference page for posixtostrc().

// Convert string to date
dt = asDate("28/03/2012", "%d/%m/%Y");
print dt;

will return:

        X1
28/03/2012

As we can see above, when the string is converted to a date, GAUSS keeps the display format the same as the string from which it was created.

You can change the display format with another call to asDate(). You can use any combination of the previously mentioned format specifiers. Or if you do not pass in a new format specifier, the date display format will be set to the default display format.

// Convert string to date
dt = asDate("July 01, 2006", "%B %d, %Y");
print dt;

The above code will return:

           X1
July 01, 2006

// Convert to quarter display format
dt =  asDate(dt, "%Y-Q%q")
print dt;

will return:

     X1
2006-Q3

// Convert to default display format
dt = asDate(dt);
print dt;

will return:

        X1
2006-07-01

Example 3: Change the format of a date variable#

// Load data
fname = getGAUSSHome("examples/xle_daily.xlsx");
xle = loadd(fname, "date(Date) + Volume");

// Print the first 2 observations
print "Dates in original format:";
print xle[1:2,.];

// Set date format to month/day/Year
xle_2 = asDate(xle, "%m/%d/%Y", "Date");

// Print the first 2 observations
print "";
print "Dates in new format:";
print xle_2[1:2,.];

The above code will print out:

Dates in original format:
            Date          Volume
      2017-06-13        15807900
      2017-06-14        30280200

Dates in new format:
            Date          Volume
      06/13/2017        15807900
      06/14/2017        30280200

Remarks#

You can find a list of the available date format specifiers in the Command Reference entry for posixtostrc().