R programming

Question

[anjalivasudevan98]

Hey everyone,

So I have a dataframe with two columns, one being a list of antibiotics and another one quantity. I have an excel sheet from which I'm extracting the concentration of drugs, say something like 100mg. I then split 100 mg to 100 and mg seperately and wanna add the 100 to the quantity column of the dataframe. This works fine.

Now, if I want to add another value to the same row in the same column, how do i do that?

For example: now my dataframe looks like this:

Antibiotic    quantity
azithromycin    100

And If i wanna add another 100 to the quantity, and make it like this:

Antibiotic    quantity
azithromycin    200

How do I do that? Could someone help me out please?

Many thanks in advance Anjali

Answer 1

[benformatics]

hard to say without seeing the data.frame

if it's named df and the antibiotics are row.names

## (will add 100 to every cell in the row)
df['azithromycin',] <- df['azithromycin',]+100 


## (will add 100 to first column)
df['azithromycin',1] <- df['azithromycin',1]+100 

If it's named df but there are separate columns

df$quantity[match('azithromycin',df$Antibiotic),'quantity'] <- df$quantity[match('azithromycin',df$Antibiotic),'quantity']+100

In all cases I assume at bare minimum the column names are quantity and antibiotic

[anjalivasudevan98]

Hi thanks for this.

I tried rbind() and i guess it wokrs, so the syntax i gave is:

Prescription_concentrations_output$Quantity[2] <- rbind(Prescription_concentrations_output$Quantity[2]+200)

Answer 2

[acvill]

Using the mutate function from the dplyr package, you can add values conditionally:

# create mock dataset

df <- data.frame(Antibiotic = rep(c("azithromycin", "doxycycline", "ciprofloxacin"), each = 3),
                 quantity = rep(c(100, 200, 300), 3))

# if antibiotic is azithromycin, add 100 to quantity

df <- dplyr::mutate(df, quantity = ifelse(Antibiotic == "azithromycin",
                                          yes = quantity + 100,
                                          no = quantity))