# 3D Histogram - Labeling the Color Bar

Hi,

I’ve enclosed a photo of the 3D histogram. How do I label the colored bar?

Thank you so much!

ROOT v6.18 on MacOS 10.14.5

``````void sandbox(){

struct input_t

{
Double_t transmittance;
};

input_t input;

FILE *f = fopen("Crystal5478_360.txt","r");
char line[400];

Double_t transArray[196];

Int_t j=0;
TFile *file = new TFile("test.root","RECREATE");
for(Int_t i;fgets(&line[0],500,f);i++){
if (line[0] == '#'){
continue;
}else{
sscanf(&line[0], "%lf", &input.transmittance);
}

transArray[j]=input.transmittance;
j++;

}

float avg = 0.0;
float sum = 0.0;
int size;

size = sizeof(transArray) / sizeof(transArray[j]);

for (int i = 0; i < size; ++i){
sum += transArray[i];
}

avg = ((float)sum)/size; //or cast sum to double before division

Double_t dev[size];

for(int i = 0; i < size-1; i ++)
{
dev[i]= transArray[i] - avg;
//cout << "Deviance  " << dev[i] << "\n";
}

/*   for(int i = 0; i < 196; i ++)
{

cout <<  transArray[i] << "\n";
}*/

TH3F *hist = new TH3F("glvoxel", "Optical Transmittance", size, 0., size, 1, 0., 20., 1, 0., 20.);

//Fill the histogram to create a "sphere". CHANGE THIS!!
/*for (UInt_t i = 0; i < nZ; ++i) {
const Double_t z = zMin + i * zStep;
for (UInt_t j = 0; j < nY; ++j) {
const Double_t y = yMin + j * yStep;
for (UInt_t k = 0; k < nX; ++k) {
const Double_t x = xMin + k * xStep;
const Double_t val = 20. - (x * x + y * y + z * z);
hist->SetBinContent(k + 1, j + 1, i + 1, val*100);
}
}
}*/

for (UInt_t i = 0; i < size; ++i) {
hist->Fill(i,10,10, dev[i]);
}

hist->GetXaxis()->SetTitle("Position (mm)");
hist->GetXaxis()->SetTitleOffset(-.5);
//hist->GetWaxis()->SetTitle("Optical Transmittane Deviance");

hist->SetTitle("OT");
gStyle->SetCanvasPreferGL(1);
hist->Draw("glcolz");

TPaveLabel *title = new TPaveLabel(-1., 0.86, 1., 0.98,
"Sample 5478 (360 nm) - Position vs Optical Transmittance Deviance");

title->SetFillColor(32);
title->Draw();
}

``````

I don’t think there’s an automatic way in this case, but you can add your own text on the canvas and place it next to the scale. For instance, you could add another TPaveLabel, if you want it in a box. For just text you can use TLatex; something like:

``````  TLatex *tex = new TLatex(0.85,0.05,"title");
tex->SetNDC(1);
tex->SetTextFont(42);
tex->Draw();
``````

after drawing the histogram.

1 Like

Try:

``````   TH3F *hist = new TH3F("glvoxel", "OT;Position (mm);;;Optical Transmittane Deviance", size, 0., size, 1, 0., 20., 1, 0., 20.);
``````
1 Like

Thank you!
@couet Also, do you all know how to make the 3D histogram opaque?

I tried setting the transparency through the color palette, but that didn’t work.

`````` gStyle->SetPalette(1,0,1);
``````

I think this representation is also transparent. @tpochep may confirm .