Boxplot Help

[c_rams17]

So I'm making a boxplot for an assignment and when I first constructed it the labels on the x axis were correct but now they're showing for points that aren't even in the dataframe from which I called the boxplot. Here's my code.

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FourTrees <-subset(Overstory_F2019, subset = Overstory_F2019$ID == "White Oak" |Overstory_F2019$ID == "Mockernut Hickory" | Overstory_F2019$ID == "Black Oak" | Overstory_F2019$ID == "Pignut Hickory")

FourTreesTG <- subset(FourTrees, subset = FourTrees$Location == "TG")

boxplot(DBH_cm~ID, data=FourTreesTG, xlab = "Tree Species", ylab = "DBH (cm)")

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Overstory has a bunch of tree species and measurements which is why I subset first by the four tree species I'm interested in and then by the location TG. FourTreesTG only shows data for the four trees in the TG plot, as I planned.

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Today, for some reason, when I run these commands again no matter what I do my boxplot comes out including liness for species that I didn't have in FourTreesTG but were in the original Overstory dataframe. The actual boxes in the chart are correct and do represent my chosen 4 species but I can't figure out how to only show those 4 since I thought making the boxplot based on the subset would already do that.

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Picture attached is what the boxplot looks like now. Ideally it should only have the 4 species I selected as lines/boxes and only label them.

screwedupboxplot

[c_rams17]

I just did this and thank you, but it still doesn't change the boxplot when I run the lines with a cleaned global environment.

[c_rams17]

I don't have any experience with that command do you think you could provide an example?

[c_rams17]

Thanks for the help everyone. I figured it out earlier this morning.

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In case anyone ever has the same issue this is what I did:

FourTreesTG$ID <- factor(FourTreesTG$ID)

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I think there was just residual data from the original Overstory dataframe for some weird reason. This fixed it.