R Error: “In numerical expression has 19 elements: only the first used”

Question

I created a dataframe:

totalDeposit <- cumsum(testd$TermDepositAMT[s1$ix])

which is basically calculating cumulative sum of TermDeposit amounts in testd dataframe and storing it in total deposit. This works perfrectly ok.

I then need to calculate the average of the deposit amount and i use the following:

avgDeposit <- totalDeposit / (1:testd)

but get an error message

   Error in 1:testd : NA/NaN argument
In addition: Warning message:
In 1:testd : numerical expression has 19 elements: only the first used

testd has some 8000 observations and 19 variables.

Could someone help me get past this issue? I've attempted to locate this error message online but all i've understood so far is that 1:testd basically makes R read testd as a number which it isn't and hence i get an error message. Would simply taking mean(totalDeposit) do the trick? I tried it but the figure i get is absurd and nowhere representative of the average.

Thank you for your help.

Answer 1

The error message is, in this case, helpful.

When you say 1:N, what you're telling R is "give me the sequence of integers between 1 and N". It's from integer1 to integer2. testd isn't an integer, it's (at best) an entire vector of integers, and so R disposes of all but the first value in testd when calculating the sequence. The alternative would be either a horrible error or a set of sequences - one between 1 and the first value in testd, another between 1 and the second value in testd...and so on.

What you want instead is 1:nrow(testd), if testd is a data frame, and either 1:length(testd) or seq_along(testd) if it's a list or vector.

Based on the question, though - the need to calculate averages? - you're actually approaching this wrong, because you don't want a sequence of values, you just want one: since average = total/number of elements that went into that total, you just want 'the number of elements' - which can be retrieved simply with nrow(testd).

Answer 2

It's pretty clear that testd is a dataframe or a list since you didn't get an error from testd$. If you had a testd in which the first element were a number but it was longer than one element you would only have gotten a warning. You perhaps wanted to write:

avgDeposit <- totalDeposit / 1:nrow(testd)

... although I admit that doesn't seem very useful. At least it won't throw an error.