PLM Package - time index failure

Hello there,
I´ve got a problem when I try to create a Panel Linear Model with my dataset, with ticker as identifier and fiscal year data (only year) as time index. The code doesn't recognize the year as time index in the pdata.frame code.
I tried categorial, numerical, as date, doesn't matter, its not working.
Here is the code and the error message:

PLMRD = plm(RD/Assets~ IPO Year Relation, data = Masterthesis,
index = c("Ticker", Fiscal Year Data), model="random")

Error in pdata.frame(data, index) :
'index' can be of length 3 at the most (one index variable for individual, time, group)

panel_data <- pdata.frame(Masterthesis, index = c("Ticker", "Fiscal Year Data"))

Error in pdata.frame(Masterthesis, index = c("Ticker", "Fiscal Year Data")) :
variable 'Fiscal Year Data' does not exist (time index)

I tried everything possible with ChatGPT and my statistic professor but both couldn´t solve it.
It seems that the dataset is the problem.
I can provide a portion of my dataset if someone want´s to try.

Thanks in advance.

Hi @ChiLL
Welcome to the Community Forum.

Yes, you will get much quicker and better help if you provide us with some of your data. Run

dput(head(Masterthesis, n=10))

Then post the output here so we can take a look.