DateListPlot if condition is fulfilled

Question

This must be very simple but I could not find an appropriate answer. I have imported a huge .xlsx file with three columns: country name, date and a value and I would like to DateListPlot the values against the dates only for some countries. This is the code used:

DateListPlot[data[1 ;; 720, {"date", "value"}], PlotRange -> All, FrameLabel -> {{None, None}, {None, HoldForm[Austria]}}]

Instead of adding manually the row numbers (1;;720), I'd like to tell Mathematica to plot the date-values for rows having "Austria" on column 1.

Thanks!

Answer 1

Since you mentioned that you used SemanticImport, I'm going to assume that the result in Mathematica is a Dataset. I created some dummy data and imported it. Check your actual data against this result (you can use FullForm to see all details). If your data is significantly different, then some of the subsequent computations may not work.

data = SemanticImport[pathToFile]

data // FullForm
(*should see DateObjects and Entity["Country",...] expressions *)

You can perform sophisticated queries on Datasets, but the following is just a simple "filter". If your data doesn't actually have Entities in it, then this needs to be adjusted.

austriaData = data[Select[#Country == Entity["Country", "Austria"] &]]
(*should see a smaller Dataset restricted to just Austria*)

DateListPlot can use data in the Dataset form, but it expects just 2-value rows (date-value pairs). So, we can constrict our rows to just the plot-able data like this:

austriaData[[All, {"Date", "Value"}]]

Let's just feed that to DateListPlot:

DateListPlot[austriaData[[All, {"Date", "Value"}]]]
(*should see a plot*)

From there you can hopefully move on to adding the plot decorations that you want.

Answer 2

We first need some data to work with. I create some random data with 3 columns: Country, Date, Number

dat = Table[{RandomChoice[{"Austria", "Gemany"}], Date[], 
    RandomInteger[{0, 100}]}, {20}]

Now we may use "Select" to pull out all rows with "Austria" as the first element:

Select[dat, #[[1]] == "Austria" &]