Correlation is easily undertaken in R using the cor.test function. The arguments use = “..” specifies the handling of missing data with the options of all.obs (assumes no missing data - missing data will produce an error), complete.obs (listwise deletion), and pairwise.complete.obs (pairwise deletion); method = “..” specifies the type of correlation (pearson, spearman or kendall).

cor.test(data$bmi, data$age, method = "pearson")