artifacts {accelerometry}

R Documentation

Accelerometer Artifact Correction

Description

Corrects abnormally high count values in accelerometer data by replacing such values with the average of neighboring count values. Returns integer vector despite the average calculation often producing a decimal; this follows the convention used in the NCI's SAS programs (http://riskfactor.cancer.gov/tools/nhanes_pam).

Usage

artifacts(counts, thresh, counts_classify = NULL)

Arguments

counts	Integer vector with accelerometer count values.
thresh	Integer value specifying the smallest count value that should be considered an artifact.
counts_classify	Integer vector with accelerometer count values to base artifact classification on, but not to adjust. Mainly included for triaxial data, where you might want to define artifacts based on vertical-axis counts but then actually adjust the triaxial sum or vector magnitude counts.

Value

Integer vector equivalent to counts except where artifacts were adjusted.

References

National Cancer Institute. Risk factor monitoring and methods: SAS programs for analyzing NHANES 2003-2004 accelerometer data. Available at: http://riskfactor.cancer.gov/tools/nhanes_pam. Accessed Aug. 19, 2018.

Examples

# Load accelerometer data for first 5 participants in NHANES 2003-2004
data(unidata)

# Get data from ID number 21007
counts.part3 <- unidata[unidata[, "seqn"] == 21007, "paxinten"]

# Replace counts > 10,000 with average of neighboring values
counts.part3.corrected <- artifacts(counts = counts.part3, thresh = 10000)

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