apa_correlation_report.R

# helper function that makes a correlation 
# Computes correlation between x and y and returns a list with the
# correlation object and the text as APA states to report it
# Also, the function prints the result, you can change this behavior with silent = FALSE
# Correlation reporting in APA Style: http://my.ilstu.edu/~jhkahn/apastats.html
# Brackets of CI in APA Style: http://blog.apastyle.org/apastyle/2010/06/formatting-statistics-using-brackets.html
correlation <- function(x,y, silent = TRUE, my.method="pearson") {

  obj <- cor.test(x,y,method = my.method )
  
  apa <- paste0("r(", round(obj$parameter, 2) ,") = ", round(obj$estimate,2) , ", p < ", round(obj$p.value, 4) ,
             ", 95% CI ","[",round(obj$conf.int[1], 2), ", ", round(obj$conf.int[2], 2), "]" )
  if(silent == FALSE) cat(apa)
  return(list(cor = obj, text = apa))
  }