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Contour Plot Maker

Map results (Z) measured under two conditions (X, Y) such as temperature and pressure as color bands and contour lines. Scattered points are triangulated and interpolated, so experimental data can be used as is - no grid needed.

1Data Table

Paste a table copied from Excel into a cell (Ctrl+V). Click a column header (A, B…) before pasting to use the first line as column names. Double-click a header to rename it, right-click to insert/delete rows and columns, and formulas such as =A1*2 work too.

2Contour Plot Options

How to make a contour plot

  1. Copy the three numeric columns X, Y and Z together with the header (one row = one measurement point).
  2. Click the column header (A) in the data table and paste - the first line becomes the column name. You can also open a CSV or Excel file.
  3. Choose the X-axis, Y-axis and Z (contour value) columns.
  4. Press Draw and use the color bands, contour lines and color bar to find the high and low regions.

What is a contour plot?

A contour plot shows the value (Z) at each position (X, Y) of a plane with lines joining equal values (contours) and colors. Like the contour lines on a map it reveals peaks (high values) and valleys (low values) at a glance, which makes it popular for studying how two process conditions affect a result.

How it is calculated

The points are joined by a Delaunay triangulation, and values inside each triangle are linearly interpolated from its three corners (the same method as matplotlib tricontourf). Contour levels split the Z range into about 14 tidy steps, colored with the viridis colormap.

The area outside the points (outside their convex hull) is not filled.

How to read a contour plot

  • Bright (yellow) areas have high Z and dark (purple) areas low Z. The closer the contour lines, the faster the value changes.
  • The automatic interpretation looks at how Z relates to the distance from the data center (R² of 0.3 or more) and reports whether the center or the edges are higher.
  • Contours where points are sparse are interpolated and may differ from reality - measure that area more if needed.

Frequently asked questions

Does my data need to be on a grid?

No. Scattered points are fine. Each row needs X, Y and Z values; rows with any blank are skipped.

How many points do I need?

The plot works from 3 points, but 20 or more are recommended to see the shape.

What appears when I hover?

The magnet cursor snaps to the nearest actual point and shows its X, Y and Z values.

Is my data sent to a server?

No. Everything is processed inside your browser and nothing is transmitted or stored.

Other chart tools

Heatmap MakerColor a table such as equipment × time slot to see high and low values at a glance.3D Surface Plot MakerDraw table data like a heatmap as a 3D surface with real height.Scatter Plot MakerPlot the relationship between two variables with a trendline, equation and R².

Need process capability, control charts or DOE?

The Qstat desktop program offers about 250 analysis features: histograms and box plots plus process capability (Cp, Cpk), control charts, measurement system analysis (MSA), design of experiments (DOE), regression and machine learning.

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