oneHot

Purpose

Returns a matrix of one-hot (indicator) variables from a vector or dataframe column.

Format

X_oh = oneHot(X)

Parameters:

X (Nx1 vector, or dataframe) – The independent variable.

Returns:

X_oh – An nobs x nclasses dataframe with indicator variables for each class in X.

Examples

// Create a categorical dataframe column
s = "good" $| "fair" $| "poor" $| "fair";
X = asdf(s, "rating");

print X;

rating
  good
  fair
  poor
  fair

// Create one-hot matrix
X_oh = oneHot(X);
print X_oh;

rating_fair      rating_good      rating_poor
      0.000            1.000           0.000
      1.000            0.000           0.000
      0.000            0.000           1.000
      1.000            0.000           0.000

y = { 2, 2, 1, 3, 3 };

y_oh = oneHot(y);

After the above code:

   X_1      X_2      X_3
0.0000   1.0000   0.0000
0.0000   1.0000   0.0000
1.0000   0.0000   0.0000
0.0000   0.0000   1.0000
0.0000   0.0000   1.0000

Remarks

1. Each column will be asigned a variable name that is the original variable name (or X if the variable passed in is not a dataframe) plus an underscore and the category. Examples are shown above.

2. If numeric data is passed to onehot(), one-hot vectors will be created for each unique value in the column. The function will not assume that intermediate numbers should be filled in. For example, a vector with the unique values 1, 2 and 4 would create a return matrix with 3 one-hot vectors.

See also

Functions design(), getcollabels(), recodecatlabels()