strtof¶

Purpose¶

Converts a string array to a numeric matrix, or a categorical / string column of a dataframe to a numeric column.

Format¶

x = strtof(sa)¶

Parameters:: sa (NxK string array) – numeric data.
Returns:: x (NxK matrix) – converted string array.

Examples¶

Example 1: Convert a string dataframe column to a numeric variable¶

Our first step will be to create a dataframe with one variable that contains numbers inside of strings.

// Create a 3x1 string array
sa = "0.9" $| "2.3" $| "1.7";

// Convert the string array to a dataframe
// with one variable named "GDP"
df_sa = asdf(sa, "GDP");

print df_sa;

The above code will print:

GDP
9
3
7

Our next step will be to convert the string labels in this dataframe to real numbers with strtof():

// Convert the strings to real numbers
df_num = strtof(df_sa[.,"GDP"]);

print df_num;

The above code will print the following output, showing us that the data is now numeric.

Example 2: Convert a string array to a numeric matrix¶

// Create a string array
string sa = { "1.1" "2.2" "3.3",
              "4.4" "5.5" "6.6" };
num = strtof(sa);

After the code above, num is a numeric matrix with the following values:

1.100  2.200 3.300
4.400  5.500 6.600

Remarks¶

Elements with more than one numerical character separated by a delimiter such as a comma or a space will be interpreted as complex data. For example, the string:

"1.2 1.9"

will be converted into the number:

1.2 + 1.9i

Parentheses surrounding the numerical elements in the string will be ignored as will be a following i. The following strings will be interpreted as the same by strtof().

"(2.31 4.72)""2.31 4.73""2.31,4.73i"