# Extract School-Level Covariates

### Description

Given a vector of variables of interest for students in a single school, extracts a single value for the school

### Usage

1 | ```
agg(x)
``` |

### Arguments

`x` |
a vector containing student-level observations for a school. If it is a factor it must contain only a single level. |

### Details

If the input is numeric, `agg`

returns the mean; if the input is not numeric, an error will be thrown unless all values are the same, in which case the single unique value will be returned.

### Value

A single value of the same type as the input vector.

### Author(s)

Luke Keele, Penn State University, ljk20@psu.edu

Sam Pimentel, University of Pennsylvania, spi@wharton.upenn.edu

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