Concatenating Strings

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5.3.1 Concatenating Strings

It has been shown above that strings can be concatenated using matrix notation (see Strings, Character Arrays). Apart from that, there are several functions to concatenate string objects: char, strvcat, strcat and cstrcat. In addition, the general purpose concatenation functions can be used: see cat, horzcat and vertcat.

All string concatenation functions except cstrcat convert numerical input into character data by taking the corresponding ASCII character for each element, as in the following example:
```
          char([98, 97, 110, 97, 110, 97])
               => ans =
                 banana
     
```

char and strvcat concatenate vertically, while strcat and cstrcat concatenate horizontally. For example:

          char("an apple", "two pears")
               => ans =
                 an apple
                 two pears
          
          strcat("oc", "tave", " is", " good", " for you")
               => ans =
                 octave is good for you

char generates an empty row in the output for each empty string in the input. strvcat, on the other hand, eliminates empty strings.

          char("orange", "green", "", "red")
               => ans =
                 orange
                 green
          
                 red
          
          strvcat("orange", "green", "", "red")
               => ans =
                 orange
                 green
                 red

All string concatenation functions except cstrcat also accept cell array data (see Cell Arrays). char and strvcat convert cell arrays into character arrays, while strcat concatenates within the cells of the cell arrays:

          char({"red", "green", "", "blue"})
               => ans =
                 red
                 green
          
                 blue
          
          strcat({"abc"; "ghi"}, {"def"; "jkl"})
               => ans =
                 {
                   [1,1] = abcdef
                   [2,1] = ghijkl
                 }

strcat removes trailing white space in the arguments (except within cell arrays), while cstrcat leaves white space untouched. Both kinds of behavior can be useful as can be seen in the examples:

          strcat(["dir1";"directory2"], ["/";"/"], ["file1";"file2"])
               => ans =
                 dir1/file1
                 directory2/file2
          
          cstrcat(["thirteen apples"; "a banana"], [" 5$";" 1$"])
               => ans =
                 thirteen apples 5$
                 a banana        1$

Note that in the above example for cstrcat, the white space originates from the internal representation of the strings in a string array (see Character Arrays).

— Built-in Function: char (x)
— Built-in Function: char (x, ...)
— Built-in Function: char (s1, s2, ...)
— Built-in Function: char (cell_array)

Create a string array from one or more numeric matrices, character matrices, or cell arrays. Arguments are concatenated vertically. The returned values are padded with blanks as needed to make each row of the string array have the same length. Empty input strings are significant and will concatenated in the output.
For numerical input, each element is converted to the corresponding ASCII character. A range error results if an input is outside the ASCII range (0-255).
For cell arrays, each element is concatenated separately. Cell arrays converted through char can mostly be converted back with cellstr. For example,
          char ([97, 98, 99], "", {"98", "99", 100}, "str1", ["ha", "lf"])
               => ["abc    "
                   "       "
                   "98     "
                   "99     "
                   "d      "
                   "str1   "
                   "half   "]
     
See also: strvcat, cellstr.

— Built-in Function: strvcat (x)
— Built-in Function: strvcat (x, ...)
— Built-in Function: strvcat (s1, s2, ...)
— Built-in Function: strvcat (cell_array)

Create a character array from one or more numeric matrices, character matrices, or cell arrays. Arguments are concatenated vertically. The returned values are padded with blanks as needed to make each row of the string array have the same length. Unlike char, empty strings are removed and will not appear in the output.
For numerical input, each element is converted to the corresponding ASCII character. A range error results if an input is outside the ASCII range (0-255).
For cell arrays, each element is concatenated separately. Cell arrays converted through strvcat can mostly be converted back with cellstr. For example,
          strvcat ([97, 98, 99], "", {"98", "99", 100}, "str1", ["ha", "lf"])
               => ["abc    "
                   "98     "
                   "99     "
                   "d      "
                   "str1   "
                   "half   "]
     
See also: char, strcat, cstrcat.

— Function File: strcat (s1, s2, ...)

Return a string containing all the arguments concatenated horizontally. If the arguments are cells strings, strcat returns a cell string with the individual cells concatenated. For numerical input, each element is converted to the corresponding ASCII character. Trailing white space is eliminated. For example,
          s = [ "ab"; "cde" ];
          strcat (s, s, s)
               => ans =
                  "ab ab ab "
                  "cdecdecde"
     
          s = { "ab"; "cde" };
          strcat (s, s, s)
               => ans =
                  {
                    [1,1] = ababab
                    [2,1] = cdecdecde
                  }
     
See also: cstrcat, char, strvcat.

— Function File: cstrcat (s1, s2, ...)

Return a string containing all the arguments concatenated horizontally. Trailing white space is preserved. For example,
          cstrcat ("ab   ", "cd")
               => "ab   cd"
     
          s = [ "ab"; "cde" ];
          cstrcat (s, s, s)
               => ans =
                  "ab ab ab "
                  "cdecdecde"
     
See also: strcat, char, strvcat.