Created a new file rntuple_histogram.js

demo/node/rntuple_histogram.js

@@ -0,0 +1,63 @@
+import { rntupleProcess } from '../../modules/rntuple.mjs';
+import { openFile, TSelector, createHistogram, makeSVG } from 'jsroot';
+import { writeFileSync } from 'fs';
+
+const selector = new TSelector();
+selector.hist = null;
+selector.minpy = null;
+selector.maxpy = null;
+selector.sum = 0;
+selector.count = 0;
+
+selector.Begin = function() {
+  this.hist = createHistogram('TH1F', 10, -5, 5);
+  this.hist.fXaxis.fXmin = -5;
+  this.hist.fXaxis.fXmax = 5;
+  this.hist.fFillColor = 2;         // Red fill
+  this.hist.fFillStyle = 1001;      // Solid
+  this.hist.fName = 'h1';
+  this.hist.fTitle = 'myDouble Distribution';
+  this.hist.fXaxis.fTitle = 'myDouble';
+  this.hist.fYaxis.fTitle = 'Entries';
+  this.hist.fXaxis.fLabelSize = 0.02;
+  this.hist.fYaxis.fLabelSize = 0.02;
+};
+
+selector.Process = function() {
+  const val = this.tgtobj.myDouble;
+
+  if (typeof val === 'number') {
+      this.hist.Fill(val);   // Fill histogram
+      this.sum += val;       // Sum for mean
+      this.count++;          // Count    
+  } else 
+    console.warn('Invalid myDouble:', val);
+};
+
+selector.Terminate = async function() {
+  if (this.count === 0) 
+    console.error('No valid entries processed');
+
+  const mean = this.sum / this.count;
+  console.log(`Mean = ${mean.toFixed(4)} from ${this.count} entries`);
+
+  const svg = await makeSVG({
+    object: this.hist,
+    width: 800,
+    height: 600
+  });
+
+  writeFileSync('myDouble_histogram.svg', svg);
+  console.log('Histogram written to myDouble_histogram.svg');
+};
+
+if (typeof window === 'undefined') {
+  openFile('./simple.root')
+    .then(file => file.readObject('myNtuple'))
+    .then(rntuple => {
+      if (!rntuple) throw new Error('myNtuple not found');
+      return rntupleProcess(rntuple, selector);
+    })
+    .then(() => console.log('RNTuple::Process finished'))
+    .catch(err => console.error(err));
+}