timeSeriesFromCSV¶

This macro illustrates the use of the time axis on a TGraph with data read from a text file containing the SWAN usage statistics during July 2017.

Author: Danilo Piparo, Olivier Couet
This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Tuesday, November 29, 2022 at 11:17 AM.

Open the data file. This csv contains the usage statistics of a CERN IT service, SWAN, during two weeks. We would like to plot this data with ROOT to draw some conclusions from it.

In [1]:
TString dir = gROOT->GetTutorialDir();
dir.Append("/graphs/");
dir.ReplaceAll("/./", "/");
FILE *f = fopen(Form("%sSWAN2017.dat", dir.Data()), "r");


Create the time graph

In [2]:
auto g = new TGraph();
g->SetTitle("SWAN Users during July 2017;Time;Number of Sessions");


Read the data and fill the graph with time along the X axis and number of users along the Y axis

In [3]:
char line[80];
float v;
char dt[20];
int i = 0;
while (fgets(line, 80, f)) {
sscanf(&line[20], "%f", &v);
strncpy(dt, line, 18);
dt[19] = '\0';
g->SetPoint(i, TDatime(dt).Convert(), v);
i++;
}
fclose(f);


Draw the graph

In [4]:
auto c = new TCanvas("c", "c", 950, 500);
c->SetLeftMargin(0.07);
c->SetRightMargin(0.04);
c->SetGrid();
g->SetLineWidth(3);
g->SetLineColor(kBlue);
g->Draw("al");
g->GetYaxis()->CenterTitle();


Make the X axis labelled with time.

In [5]:
auto xaxis = g->GetXaxis();
xaxis->SetTimeDisplay(1);
xaxis->CenterTitle();
xaxis->SetTimeFormat("%a %d");
xaxis->SetTimeOffset(0);
xaxis->SetNdivisions(-219);
xaxis->SetLimits(TDatime(2017, 7, 3, 0, 0, 0).Convert(), TDatime(2017, 7, 22, 0, 0, 0).Convert());
xaxis->SetLabelSize(0.025);
xaxis->CenterLabels();


Draw all canvases

In [6]:
%jsroot on
gROOT->GetListOfCanvases()->Draw()