How to plot week number with string and control xtics increment using Gnuplot?

Question

How do I plot this time samples with a string (W) inside (column 3) ?

And How do I control xtics increment with time format ?

Few lines of Data :

France,FR,2020-W09,118,3318,67012883,4.95128675481698,3.55635925256178,TESSy
France,FR,2020-W10,996,11101,67012883,16.5654714482288,8.97216466984956,TESSy
France,FR,2020-W11,4297,29623,67012883,44.2049329529667,14.5056206326166,TESSy
France,FR,2020-W12,10595,73235,67012883,109.28495644636,14.4671263740015,TESSy
France,FR,2020-W13,24156,122870,67012883,183.35280396756,19.6598030438675,TESSy
France,FR,2020-W14,30304,127029,67012883,189.55907329043,23.8559698966378,TESSy
France,FR,2020-W15,24925,140316,67012883,209.386604065371,17.7634767239659,TESSy

My script :

#https://www.ecdc.europa.eu/en/publications-data/covid-19-testing

#Data (105,77K) here :
system("wget https://opendata.ecdc.europa.eu/covid19/testing/csv -P $PWD -O testing.csv")

reset
set term wxt font ',11' size 1200,800

set datafile separator ","
set grid
#set key at screen 0.9, 0.9


timefmt = "%Y-%s%W"
set xdata time
set xtics format timefmt timedate rotate by -45
SECPERWEEK = 3600.*24.*7.
Y_W(col) = timecolumn(col,timefmt) + SECPERWEEK * (strcol(col)[2:3] - 1)

plot '< grep France testing.csv' u (Y_W(3)):4 notitle w l

Thank you

question from:https://stackoverflow.com/questions/65599181/how-to-plot-week-number-with-string-and-control-xtics-increment-using-gnuplot

Answer 1

The basic error is that the Y_W function is looking in the wrong columns for the week number. It should be substring 7 to 8 not 2 to 3.

Y_W(col) = timecolumn(col,"%Y") + SECPERWEEK * (strcol(col)[7:8])

As explained by theozh in this answer, gnuplot uses American week numbers by default, not ISO 8601, so I have not addressed that here.