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github-actions[bot] edited this page Mar 18, 2026 · 4 revisions

Live Mode Guide

FastPlot supports live data visualization by polling a .mat file for updates and auto-refreshing the display. Live mode works with single plots, tiled dashboards, and tabbed docks.

Basic Live Plot

setup;

% Create initial plot
fp = FastSense('Theme', 'dark');
x = linspace(0, 10, 1e5);
y = sin(x) + 0.1 * randn(size(x));
fp.addLine(x, y, 'DisplayName', 'Sensor');
fp.addThreshold(0.8, 'Direction', 'upper', 'ShowViolations', true);
fp.render();

% Start polling
fp.startLive('data.mat', @(fp, s) fp.updateData(1, s.x, s.y));

The callback @(fp, s) fp.updateData(1, s.x, s.y) is called every poll cycle:

  • fp — the FastSense instance
  • s — struct loaded from the .mat file
  • fp.updateData(lineIdx, newX, newY) — replaces line data and re-renders

Stopping Live Mode

fp.stopLive();

Or use the Live Mode button in the toolbar.

View Modes

Control how the view updates when new data arrives:

Mode Behavior
'preserve' Keep current zoom/pan position. User's view is not disturbed
'follow' Scroll X-axis to show the latest data. Good for monitoring
'reset' Zoom to show all data. Good for overview 
fp.startLive('data.mat', @updateFcn, 'ViewMode', 'follow');

Change view mode while running:

fp.setViewMode('follow');
fp.setViewMode('preserve');

Polling Interval

Default is 2 seconds. Adjust with the 'Interval' option:

fp.startLive('data.mat', @updateFcn, 'Interval', 0.5);  % Poll every 500ms
fp.startLive('data.mat', @updateFcn, 'Interval', 5);     % Poll every 5 seconds

Live Dashboard

FastSenseGrid supports live mode across all tiles:

fig = FastSenseGrid(2, 2, 'Theme', 'dark');

fp1 = fig.tile(1); fp1.addLine(x, y1, 'DisplayName', 'Pressure');
fp2 = fig.tile(2); fp2.addLine(x, y2, 'DisplayName', 'Temperature');
fp3 = fig.tile(3); fp3.addLine(x, y3, 'DisplayName', 'Flow');
fp4 = fig.tile(4); fp4.addLine(x, y4, 'DisplayName', 'Vibration');

fig.renderAll();

% Start live mode on the entire dashboard
fig.startLive('sensors.mat', @(fig, s) updateDashboard(fig, s), ...
    'Interval', 2, 'ViewMode', 'follow');

Update callback for dashboard:

function updateDashboard(fig, s)
    fig.tile(1).updateData(1, s.t, s.pressure);
    fig.tile(2).updateData(1, s.t, s.temperature);
    fig.tile(3).updateData(1, s.t, s.flow);
    fig.tile(4).updateData(1, s.t, s.vibration);
end

Live Mode with Metadata

Attach metadata that updates on each poll:

fp.startLive('data.mat', @updateFcn, ...
    'MetadataFile', 'meta.mat', ...
    'MetadataVars', {'units', 'calibration'});

Live Event Detection

Combine live mode with event detection for real-time monitoring:

% Create sensor and resolve
s = Sensor('pressure', 'Name', 'Pressure');
s.X = x; s.Y = y;
sc = StateChannel('machine');
sc.X = [0 30 60]; sc.Y = [0 1 2];
s.addStateChannel(sc);
s.addThresholdRule(struct('machine', 1), 70, 'Direction', 'upper', 'Label', 'Run HI');
s.resolve();

% Configure event detection with live logging
cfg = EventConfig();
cfg.MinDuration = 0.5;
cfg.OnEventStart = eventLogger();
cfg.addSensor(s);

% Plot
fp = FastSense('Theme', 'dark');
fp.addSensor(s, 'ShowThresholds', true);
fp.render();

% Start live polling
fp.startLive('pressure_data.mat', @(fp, data) updateWithDetection(fp, data, cfg));

Octave Compatibility

GNU Octave does not support MATLAB timers. Use runLive() for a blocking poll loop:

fp.render();

% Blocking loop — press Ctrl+C to stop
fp.LiveFile = 'data.mat';
fp.LiveUpdateFcn = @(fp, s) fp.updateData(1, s.x, s.y);
fp.runLive();

For dashboards:

fig.renderAll();
fig.LiveFile = 'data.mat';
fig.LiveUpdateFcn = @myUpdateFcn;
fig.runLive();

Manual Refresh

Trigger a one-shot data reload without starting continuous polling:

fp.refresh();
fig.refresh();

Toolbar Integration

The FastSenseToolbar provides a Live Mode button:

tb = FastSenseToolbar(fp);
% Click the Live Mode button to toggle polling on/off
% Or programmatically:
tb.toggleLive();

The Refresh button triggers a manual one-shot reload:

tb.refresh();

Tips

  • Set 'ViewMode', 'follow' for monitoring use cases where you always want to see the latest data
  • Use 'preserve' when users need to zoom into historical data while live updates continue
  • Keep polling interval reasonable (1-5 seconds) to avoid overwhelming the file system
  • The .mat file should be written atomically (write to temp file, then rename) to avoid partial reads
  • Live mode works with linked axes — all linked plots update together

See Also

FastSense Wiki

API Reference

Guides

Use Cases

Internals

Resources

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