How do I make a simple graph with subset factor and two variables? (help pls)

My data contains the Years of sampling / Site (with 6 different sites)/ and 3 different chemical parameters

I want to create a simple graph with the year on the X and Nitrate on the Y for one site in particular ...

I don't know what code to use, I tried this
plot(Allsites_data$Nitrate~Allsites_data$Year) but it doesn't classify the site I want... Thanks!

Try subsetting the data.

     dat1  <-  subset(Allsites_data, Site == "Brownstown")

Then graph dat1

Rince and repeat for each value of Site
There are other ways and probably better ones but this should work in base R

For future reference, here are some hints on asking questions in the forum.

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Thanks a mil for that!

Building on @jkrideau's response a little bit, to get the plot in a single command using base R (plot and subset):

plot(x = subset(Allsites_data$Year, Allsites_data$Site == "Brownstone"),
     y = subset(Allsites_data$Nitrate, Allsites_data$Site == "Brownstone"))

The kicker is this may not give you quite what you want depending on the data type of Year in the data frame (which is one of the reasons a reproducible example is nice to have). If Year is numeric, then you may see things like "2011.5" in the x-axis of a dot plot.

If, instead, Year is a factor, you may get a y-axis that is more what you expected, and you will likely get a boxplot instead of a dot plot.

Depending on what you're looking for, specifically, you may need to do a little bit of light work on the data frame or do some additional formatting work within plot() (or, potentially, consider switching over and using ggplot(), but my sense is that you're not looking to dive into that world).

Good luck!

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Thanks so much, really helped !!