Instruction: Write a command to add a new column to a data frame that calculates the logarithm of an existing column 'A'.
Context: This question checks the candidate's proficiency with basic data frame operations in R. Adding computed columns is a common task in data preparation and analysis, and familiarity with such operations is crucial for efficient data handling.
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First, to address the question directly, the command to add a new column that calculates the logarithm of an existing column 'A' in a data frame, let's call this data frame df, would be written in R as follows: df$new_column <- log(df$A)
This command uses the log() function, which computes the natural logarithm of a given number or array. In this case, df$A references the column 'A' of the data frame df. The result of log(df$A) is then assigned to a new column in the data frame, df$new_column....