Show Heatmap value under mouse #1787

tonpimenta · 2022-04-19T19:56:51Z

tonpimenta
Apr 19, 2022

Hello Community!
Is there a way to present the heatmap value together with the Crosshair, besides X and Y coordinate?
Thanks
Wellington

Answered by swharden

May 1, 2022

The MouseTracker demo shows how to use events to display information about where the mouse/crosshair is

ScottPlot/src/ScottPlot4/ScottPlot.Demo/ScottPlot.Demo.WinForms/WinFormsDemos/MouseTracker.cs

Lines 1 to 62 in ec3c241

     ﻿using System;  
   using System.Collections.Generic;  
   using System.ComponentModel;  
   using System.Data;  
   using System.Drawing;  
   using System.Linq;  
   using System.Text;  
   using System.Threading.Tasks;  
   using System.Windows.Forms;  
   using ScottPlot.Plottable;  
    
   namespace ScottPlot.Demo.WinForms.WinFormsDemos  
   {  
   public partial class MouseTracker : Form  
   {  
   private readonly Crosshair Crosshair;  
    
   public 

View full answer

swharden · 2022-05-01T19:57:08Z

swharden
May 1, 2022
Maintainer

The MouseTracker demo shows how to use events to display information about where the mouse/crosshair is

ScottPlot/src/ScottPlot4/ScottPlot.Demo/ScottPlot.Demo.WinForms/WinFormsDemos/MouseTracker.cs

Lines 1 to 62 in ec3c241

    
           ﻿using System; 
        
           using System.Collections.Generic; 
        
           using System.ComponentModel; 
        
           using System.Data; 
        
           using System.Drawing; 
        
           using System.Linq; 
        
           using System.Text; 
        
           using System.Threading.Tasks; 
        
           using System.Windows.Forms; 
        
           using ScottPlot.Plottable; 
        
           namespace ScottPlot.Demo.WinForms.WinFormsDemos 
        
           { 
        
               public partial class MouseTracker : Form 
        
               { 
        
                   private readonly Crosshair Crosshair; 
        
                   public MouseTracker() 
        
                   { 
        
                       InitializeComponent(); 
        
                       formsPlot1.Plot.AddSignal(DataGen.RandomWalk(null, 100)); 
        
                       Crosshair = formsPlot1.Plot.AddCrosshair(0, 0); 
        
                       formsPlot1_MouseLeave(null, null); 
        
                       lblMouse.Text = "Mouse has yet to enter the plot..."; 
        
                   } 
        
                   private void formsPlot1_MouseMoved_1(object sender, MouseEventArgs e) 
        
                   { 
        
                       (double coordinateX, double coordinateY) = formsPlot1.GetMouseCoordinates(); 
        
                       XPixelLabel.Text = $"{e.X:0.000}"; 
        
                       YPixelLabel.Text = $"{e.Y:0.000}"; 
        
                       XCoordinateLabel.Text = $"{coordinateX:0.00000000}"; 
        
                       YCoordinateLabel.Text = $"{coordinateY:0.00000000}"; 
        
                       Crosshair.X = coordinateX; 
        
                       Crosshair.Y = coordinateY; 
        
                       formsPlot1.Refresh(lowQuality: true, skipIfCurrentlyRendering: true); 
        
                   } 
        
                   private void formsPlot1_MouseEnter(object sender, EventArgs e) 
        
                   { 
        
                       lblMouse.Text = "Mouse ENTERED the plot"; 
        
                       Crosshair.IsVisible = true; 
        
                   } 
        
                   private void formsPlot1_MouseLeave(object sender, EventArgs e) 
        
                   { 
        
                       lblMouse.Text = "Mouse LEFT the plot"; 
        
                       XPixelLabel.Text = $"--"; 
        
                       YPixelLabel.Text = $"--"; 
        
                       XCoordinateLabel.Text = $"--"; 
        
                       YCoordinateLabel.Text = $"--"; 
        
                       Crosshair.IsVisible = false; 
        
                       formsPlot1.Refresh(); 
        
                   } 
        
               } 
        
           }

Briefly you can configure your window to call a MouseMoved() function whenever the mouse moves, and in that function use GetMouseCoordinates() to determine where the mouse is, then use math/logic to determine which heatmap square that corresponds to and display that value.

That functionality is not built into the heatmap currently, but it could be. I'll create an issue (#1822) to track progress on this front

8 replies

tonpimenta May 3, 2022
Author

and thank you for providing us with this great tool that ScottPlot is. With it, we could do on C# things that we thought impossible (Im not exaggerating). We're clinical medical physicists with little programming background and not much free time to study it... and we're trying to improve quality of care by creating our own tools that leverage a recent API that allows us to access our Radiotherapy systems and do cooler stuff! haha

KATAMANENI May 5, 2022

Dear @swharden

I do have another requirement related to heatmap display. My data is in the range of (Xmin to Xmax) but it must be displayed as (scaleXmin to scaleXmax). The scaling factor here is mostly 0.1 to 0.01). For example, my data can be 0 to 10000 but I wish to display it as 0 to 100% ( scale factor = 0.01). Even the colour bar must display the range from 0 to 100 instead of 0 to 10000 and, as shown above, the value under mouse also must be displayed as 55.5(for an actual value of 5550) . One way is to scale down the data before passing it on to the heatmap, but it is expensive to do this several 1000 times as the data is not readily available and would be built in real-time using sensors.

Could you suggest a way to achieve it? Basically, there must be a ScaleFactor property that I can set to be applied to the data, similar CellWidth and CellHeight.

Thank you

swharden May 5, 2022
Maintainer

Hi @KATAMANENI,

I thin you can achieve this by using a custom function to control the labels shown on the colorbar.

var plt = new ScottPlot.Plot(600, 400);
var cb = plt.AddColorbar(ScottPlot.Drawing.Colormap.Turbo);
Func<double, string> tickFormatter = (y) => $"{y * .01}";
cb.AutomaticTicks(formatter: tickFormatter);

KATAMANENI May 6, 2022

Excellent. This way I can control the ticks.
How about the data scaling? What data ranges does the heatmap use? As explained, for example, my data range is from -8192 to +8192 but should be drawing them as -100 to +100. What properties should I be using for this?

Thank you

swharden May 6, 2022
Maintainer

ScottPlot.Plot plt = new(600, 400);

// sample data containing values from -8192 to +8192
double[,] data = ScottPlot.DataGen.Random2D(
    rand: new Random(0),
    rows: 123,
    columns: 123,
    multiplier: 8192 * 2,
    offset: -8192);

var hm = plt.AddHeatmap(data, ScottPlot.Drawing.Colormap.Turbo);
var cbar = plt.AddColorbar(hm);

// create a custom tick formatter to scale [-8192, 8192] to [-100, 100]
Func<double, string> tickFormatter = (y) => $"{y / 81.92:N0}";
cbar.AutomaticTicks(formatter: tickFormatter);

plt.SaveFig("test.png");

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	using System;
	using System.Collections.Generic;
	using System.ComponentModel;
	using System.Data;
	using System.Drawing;
	using System.Linq;
	using System.Text;
	using System.Threading.Tasks;
	using System.Windows.Forms;
	using ScottPlot.Plottable;

	namespace ScottPlot.Demo.WinForms.WinFormsDemos
	{
	public partial class MouseTracker : Form
	{
	private readonly Crosshair Crosshair;

	public

Show Heatmap value under mouse #1787

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tonpimenta Apr 19, 2022

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swharden May 1, 2022 Maintainer

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KATAMANENI May 6, 2022

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tonpimenta
Apr 19, 2022

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swharden
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