# Adding a sequential column to R

I'm sorry if this question is disgustingly simple, but I'm looking for a way to just add a column of consecutive integers to the dataframe (assuming there are 200 observations in my dataframe, for example starting at 1 for the first observation and ending at 200 for the last).

How can i do this?

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2 answers

For dataframe (df) you can use

```
df$observation <- 1:nrow(df)
```

but if you have a matrix you prefer to use

```
ma <- cbind(ma, "observation"=1:nrow(ma))
```

as using the first parameter will convert your data to a list.

Source: http://r.789695.n4.nabble.com/adding-column-of-ordered-numbers-to-matrix-td2250454.html

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