Append covariate data as a column within a table

append.covariate appends a data frame of covariates as a new column in a data frame of trait data. In the event a trait has several covariates available, the first one found (i.e. lowest row number) will take precedence

append.covariate(data, column.name, covariates.data)

Arguments

data	trait dataframe that will be appended to.
column.name	name of the covariate as it will appear in the appended column
covariates.data	one or more tables of covariate data, ordered by the precedence they will assume in the event a trait has covariates across multiple tables. All tables must contain an 'id' and 'level' column, at minimum.