The QRI_plot() is used to plot Quantile Regression Index (QRI) and generate the normative curves for individual's regional brain imaging metrics.
QRI_plot(x, y, xlab, ylab, DXcontrol, data)the x coordinate for the QRI plot
the y coordinate for the QRI plot
the label for the x coordinate
the label for the y coordinate
the expected aging trajectory. It should only be calculated from the controls(i.e. DXcontrol='control==0'). If DXcontrol=NULL, the expected aging trajectory will be calculated from the full data.
a data frame contains the predictor(x coordinate), response(y coordinate) and control(DXcontrol) in the quantile regression model.
This function returns a plot for individual measurements.
The QRI score can be used as an alternative to BrainAge to assess accelerated brain aging by determining an individuals' placement on the expected aging trajectory.A study by Ryan et al (2020) demonstrated that QRI and BrainAge share up to 80% of the variance in both patients and controls. The typical function usage involves calling the QRI function with the following parameters (age, sex) on a list of tissue-specific neuroimaging traits such as regional white matter fractional anisotropy, regional gray matter cortical thickness, or gray matter subcortical volumes. Quantile regression is performed using the controls (DXcontrol='control==0') to generate the normative curves for the 5th, 50th, and 95th percentiles. Then each patient (DXcontrol='control==1') and control<U+2019>s individual (DXcontrol='control==0') data is compared to the expected aging trajectory. Each regional measure is assigned a score based upon its location: values > 95% of the expected age data are assigned a value of <U+201C>-1<U+201D>; values < 5% receive a value of <U+201C>1<U+201D>; all others are assigned <U+201C>0<U+201D>. The function then averages across the regional data to generate a tissue-specific QRI score (i.e. white matter QRI).
H. Wickham. ggplot2: Elegant Graphics for Data Analysis. Springer-Verlag New York, 2016.
Roger Koenker (2020). quantreg: Quantile Regression. R package version 5.61. https://CRAN.R-project.org/package=quantreg
R Core Team (2020). R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. URL https://www.R-project.org/.
# NOT RUN {
QRIplot <- QRI_plot(x='Age',y='Ventricle', xlab='Age', ylab='Ventricle', DXcontrol='Control==0',
data=QRIpkg::subcortical)
# }
Run the code above in your browser using DataLab