knitr::opts_chunk$set( collapse = TRUE, comment = "#>" ) if(!require(zscorer)) install.packages("zscorer")
Earlier versions (pre-release and v0.1.0) of zscorer
used different functions that calculated only three anthropometric indices: weight-for-age, height-for-age and weight-for-height. Also, these functions used a simplified construct of the WHO Growth Reference in which children's ages were recorded in months compared to days in the standard WHO Growth Reference.
With the developers' recent work on anthropometric data quality processes implemented in R (see nipnTK), a more consistent and standard set of functions were deemed necessary to calculate not just three but all anthropometric indices used in the WHO Growth Standards and to make the children's age in the reference data consistent with the standard using days. This work has now culminated in the current zscorer
function.
For the purposes of backwards compatibility and to keep a record of past codebase for previous versions of the functions, the legacy functions have been kept in zscorer
. This vignette describes those functions and shows examples of how to use them.
For new users of zscorer
, developers recommend to start learning and using the new functions instead of using these legacy functions. For previous zscorer
users, developers recommend to review past code that use the legacy functions and if feasible adapt code to the new functions available.
The zscorer
package comes with the original legacy functions included in its version 0.1.0
. These functions allow for the calculation of weight-for-age
, height-for-age
and weight-for-height z-scores
for individual children and for a cohort of children.
For this example, we will use the getWGS()
function and apply it to dummy data of a 52 month old male child with a weight of 14.6 kg and a height of 98.0 cm.
# weight-for-age z-score waz <- getWGS(sexObserved = 1, # 1 = Male / 2 = Female firstPart = 14.6, # Weight in kilograms up to 1 decimal place secondPart = 52, # Age in whole months index = "wfa") # Anthropometric index (weight-for-age) waz # height-for-age z-score haz <- getWGS(sexObserved = 1, firstPart = 98, # Height in centimetres secondPart = 52, index = "hfa") # Anthropometric index (height-for-age) haz # weight-for-height z-score whz <- getWGS(sexObserved = 1, firstPart = 14.6, secondPart = 98, index = "wfh") # Anthropometric index (weight-for-height) whz
Applying the getWGS()
function results in a calculated z-score
for one child.
For this example, we will use the getCohortWGS()
function and apply it to sample data anthro1
that came with zscorer
.
# Make a call for the anthro1 dataset
anthro1
As you will see, this dataset has the 4 variables you will need to use with getCohortWGS()
to calculate the z-score
for the corresponding anthropometric index. These are age
, sex
, weight
and height
.
library(zscorer)
head(anthro1)
To calculate the three anthropometric indices for all the children in the sample, we execute the following commands in R:
# weight-for-age z-score waz <- getCohortWGS(data = anthro1, sexObserved = "sex", firstPart = "weight", secondPart = "age", index = "wfa") head(waz, 50) # height-for-age z-score haz <- getCohortWGS(data = anthro1, sexObserved = "sex", firstPart = "height", secondPart = "age", index = "hfa") head(haz, 50) # weight-for-height z-score whz <- getCohortWGS(data = anthro1, sexObserved = "sex", firstPart = "weight", secondPart = "height", index = "wfh") head(whz, 50)
Applying the getCohortWGS()
function results in a vector of calculated z-scores
for all children in the cohort or sample.
For this example, we will use the getAllWGS()
function and apply it to sample data anthro1
that came with zscorer
.
# weight-for-age z-score zScores <- getAllWGS(data = anthro1, sex = "sex", weight = "weight", height = "height", age = "age", index = "all") head(zScores, 20)
Applying the getAllWGS()
function results in a data frame of calculated z-scores
for all children in the cohort or sample for all the anthropometric indices.
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