c3dr (version 0.2.0)

c3d_data: Get point data from a c3d object

Description

Get the point data of an c3d object in a data frame.

Usage

c3d_data(x, format = "wide")

Value

A data frame of class c3d_data with the c3d point data. The structure of the data frame depends on the 'format' argument.

Arguments

x

A c3d object, as imported by c3d_read().

format

Either "wide" (default), "long", or "longest" to determine the format of the resulting data frame. See the Data Formats section for more details.

Data Formats

Wide

The wide format has three numeric columns per point (x, y, z). The column names have the structure pointname_type, so for example the x-coordinate of a point named C7 has the name C7_x. Each row corresponds to one recording frame.

Long

The long format has one column per point. The column names correspond to the names of the points. Each recording frame corresponds to three rows of data (x, y, z). In additional to the point columns containing numeric data there are two additional columns: One that indicates the frame number (frame, numeric) and one that indicates the coordinate type (type, either x, y, or z, as a character).

Longest

The longest format has one data column (value, numeric). The other columns indicate the frame number (frame, numeric), the coordinate type (type, either x, y, or z, as a character), and the point name (point, character). Thus, each row of the data frame corresponds to one data entry.

Details

The point data of imported c3d objects in c3dr is saved as a list of lists. This is good for internal handling, but for analysis a table format (a data frame) is often more convenient.c3d_data() returns the point data from an imported c3d object as a data frame.

Analyses of data frames may require them to have different formats. For c3d_data output, different data formats ("wide", "long", "longest") are available. See the section below for more details. You can convert between different formats with c3d_convert().

Examples

# Import example data
d <- c3d_read(c3d_example())

# wide format (default)
w <- c3d_data(d)
head(w)

# long format
l <- c3d_data(d, format = "long")
head(l)

# longest format
ll <- c3d_data(d, format = "longest")
head(ll)