# dummybr¶

## Purpose¶

Creates a set of dummy (0/1) variables. The highest (rightmost) category is bounded on the right.

## Format¶

y = dummybr(x, v)
Parameters: x (Nx1 vector) – data that is to be broken up into dummy variables v (Kx1 vector) – specifies the $$K$$ breakpoints (these must be in ascending order) that determine the $$K$$ categories to be used. These categories should not overlap. y (NxK matrix) – containing the $$K$$ dummy variables. Each row will have a maximum of one 1.

## Examples¶

// Set seed for repeatable random numbers
rndseed 135345;

// Create uniform random integers between 1 and 9
x = ceil(9*rndu(5, 1));

// Set the breakpoints
v = { 1, 5, 7 };

dm = dummybr(x, v);


The code above produces three dummies based upon the breakpoints in the vector v:

x <= 1
1 < x <= 5
5 < x <= 7


which look like:

     0 1 0       2
0 0 0       9
dm = 0 1 0   x = 4
0 0 1       7
1 0 0       1


## Remarks¶

• Missings are deleted before the dummy variables are created.
• All categories are open on the left (i.e., do not contain their left boundaries) and are closed on the right (i.e., do contain their right boundaries). Thus, $$K$$ breakpoints are required to specify $$K$$ dummy variables.
• The function dummy() is similar to dummybr(), but in that function the highest category is unbounded on the right.

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