strindx#

Purpose#

Finds the index of one string within another string.

Format#

idx = strindx(haystack, needle[, start])#
Parameters:

  • haystack (String array, or dataframe of type category or string) – The data to be searched.

  • needles (String array or string) – The substring to be searched for in haystack. Must be ExE conformable with haystack input.

  • start (Scalar) – Optional argument, the starting point of the element-by-element search in haystack for an occurrence of needle. The index of the first character in a string is 1. Default=1.

Returns:

idx (Matrix) – Contains the index of the first occurrence of needle, within haystack, which is greater than or equal to start. If no occurrence is found, it will be 0.

Examples#

Dataframe example#

// Create file name with full path
fname = getGAUSSHome("examples/auto2.dta");

// Load 'rep78' variable
rep78 = loadd(fname, "rep78");

// Print out the first 5 observations
head(rep78);

The above code will print out:

  rep78
Average
Average
      .
Average
   Good

Now we will find the index of the start of "age".

// Find the index of "age" in 'rep78'
idx = strindx(rep78, "age");

// Print the first 5 observations of 'idx'
head(idx);

5.0000000
5.0000000
0.0000000
5.0000000
0.0000000

Dataframe example #2: Searching across multiple variables#

The strindx() procedure can also be used to search across multiple variables.

// Create file name with full path
fname = getGAUSSHome("examples/auto2.dta");

// Load 'rep78' and 'make` variable
rep78 = loadd(fname, "rep78 + make");

// Find the index of "age" in 'rep78'
// and "AMC" in 'make'
idx = strindx(rep78, "age"$~"AMC");

// Print the first 5 observations of 'idx'
head(idx);

5.0000000        1.0000000
5.0000000        1.0000000
0.0000000        1.0000000
5.0000000        0.0000000
0.0000000        0.0000000

String array example#

// Create a 3x1 string array
state = "alaska" $|
        "alabama" $|
        "arkansas";

// Find the first instance of the
// letter 'a' starting from
// the front of the string
strrindx(state, "a");

Since the search starts from the first character, the above code will print out:

1.0000000
1.0000000
1.0000000

// Find the first instance of the
// letter 'a' starting from the
// 5th character of the string
strindx(state, "a", 5);

This time, the search will start from the 5th character and continue searching towards the last character, resulting in:

6.0000000
5.0000000
7.0000000

String example#

An example of the use of this function is the location of a name within a string of names:

// String to search in
haystack = "nameagepaysex";

// String to search for
needle = "pay";

// Find starting index of 'needle'
idx = strindx(haystack, needle, 1);

The above code will set idx equal to:

8.00

This function is used with strsect() for extracting substrings.

See also

Functions strrindx(), strlen(), strsect(), strput(), strreplace()

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