plotly/plotly.js · warning

Encountered arbitrary coordinates! Unable to input data grid

Error message

Encountered arbitrary coordinates! Unable to input data grid.

What it means

processGrid in src/traces/streamtube/calc.js:206 validates that x/y/z coordinates form a regular (grid) mesh. When coordinates are 'arbitrary' — not evenly spaced / not a cartesian product along each axis — the streamtube algorithm cannot build the vector-field grid, so Plotly warns and empties the trace (empty()), rendering nothing.

Source

Thrown at src/traces/streamtube/calc.js:206

                var q100 = getIndex(i + 1, j, k);

                if(
                    !(arrK[q000] * dirK < arrK[q001] * dirK) ||
                    !(arrJ[q000] * dirJ < arrJ[q010] * dirJ) ||
                    !(arrI[q000] * dirI < arrI[q100] * dirI)
                ) {
                    arbitrary = true;
                }

                if(arbitrary) break;
            }
            if(arbitrary) break;
        }
        if(arbitrary) break;
    }

    if(arbitrary) {
        Lib.warn('Encountered arbitrary coordinates! Unable to input data grid.');
        empty();
    }

    return {
        xMin: xMin,
        yMin: yMin,
        zMin: zMin,
        xMax: xMax,
        yMax: yMax,
        zMax: zMax,
        Xs: Xs,
        Ys: Ys,
        Zs: Zs,
        len: len,
        fill: gridFill
    };
}

View on GitHub (pinned to 1d090e0b5f)

Solutions

1. Resample your data onto a regular, monotonically increasing grid before plotting.
2. Use numpy/meshgrid (or the JS equivalent) to build x/y/z from linspace ranges matching the u/v/w array shapes.
3. If the data is inherently scattered, visualize with scatter3d instead of streamtube.

Example fix

// before
x: [0, 0.3, 1], y: [0, 0.7, 1], z: [0, 0.5, 1] // irregular spacing
// after
x: [0, 0.5, 1], y: [0, 0.5, 1], z: [0, 0.5, 1] // uniform grid

function isUniformAndIncreasing(arr, eps = 1e-9) {
  const d = arr[1] - arr[0];
  if (d <= eps) return false;
  return arr.every((v, i) => i === 0 || Math.abs((arr[i] - arr[i - 1]) - d) < eps);
}
if (!isUniformAndIncreasing(x) || !isUniformAndIncreasing(y) || !isUniformAndIncreasing(z)) {
  throw new Error('streamtube requires uniformly spaced, increasing x/y/z grids');
}

function isRegularGrid(x, y, z) {
  const inc = a => a.every((v, i) => i === 0 || v > a[i - 1]);
  return inc(x) && inc(y) && inc(z) &&
    u.length === x.length * y.length * z.length;
}

When it happens

Trigger: A streamtube trace whose x, y or z arrays are not strictly increasing with uniform spacing, or whose lengths do not correspond to a rectangular grid of u/v/w samples (e.g. scattered measurement points instead of a mesh).

Common situations: Feeding raw CFD/experimental sensor data collected at irregular positions; generating coordinates from simulation output on unstructured meshes; typos causing duplicate or out-of-order coordinates.

AI-assisted analysis of plotly/plotly.js@1d090e0b5f (2026-09-02). Data as JSON: /api/errors/b88d1796e825b006. Report an issue: GitHub.