Trend

Smooth line chart

Use a smooth line chart only when the underlying data is genuinely continuous, since the spline interpolation implies values exist between your actual data points. It reads as more polished for presentations, but on weekly or monthly snapshots the smoothing can misrepresent what happened between periods. When in doubt, the straight line chart is the more honest default.

Minimal dvt spec

The panel body for a smooth line chart. Add an id and title of your own; the sample data is inline, so it renders the moment you paste it into a dvt dashboard. Point it at your warehouse by swapping that sample data for a data block whose query returns the same shape.

View spec

{
  "type": "chart:line:smooth",
  "data": {
    "rows": [
      {
        "week": "W1",
        "value": 40
      },
      {
        "week": "W2",
        "value": 52
      },
      {
        "week": "W3",
        "value": 49
      }
    ]
  },
  "spec": {
    "series": [
      {
        "type": "line",
        "smooth": true
      }
    ]
  }
}

Customize

Every control in dvt's edit tray writes a field of this spec; the variants below change the minimal spec above, and the reference below lists every control and ChartSpec field this type accepts.

Normal range and crosshair

Shade a normal range on the y-axis and switch the tooltip to a shared crosshair.

What changed

 {
   "type": "chart:line:smooth",
   "data": {
     "rows": [
       {
         "week": "W1",
         "value": 40
       },
       {
         "week": "W2",
         "value": 52
       },
       {
         "week": "W3",
         "value": 49
       }
     ]
   },
   "spec": {
     "series": [
       {
         "type": "line",
         "smooth": true
       }
-    ]
+    ],
+    "annotations": [
+      {
+        "type": "band",
+        "axis": "y",
+        "from": 45,
+        "to": 55,
+        "label": "Normal range"
+      }
+    ],
+    "tooltip": {
+      "crosshair": {
+        "axis": "x",
+        "label": true
+      }
+    }
   }
 }

Full spec

{
  "type": "chart:line:smooth",
  "data": {
    "rows": [
      {
        "week": "W1",
        "value": 40
      },
      {
        "week": "W2",
        "value": 52
      },
      {
        "week": "W3",
        "value": 49
      }
    ]
  },
  "spec": {
    "series": [
      {
        "type": "line",
        "smooth": true
      }
    ],
    "annotations": [
      {
        "type": "band",
        "axis": "y",
        "from": 45,
        "to": 55,
        "label": "Normal range"
      }
    ],
    "tooltip": {
      "crosshair": {
        "axis": "x",
        "label": true
      }
    }
  }
}

Thick line with deltas

Thicken the line, switch to a named color scheme, and label each point with its change.

What changed

 {
   "type": "chart:line:smooth",
   "data": {
     "rows": [
       {
         "week": "W1",
         "value": 40
       },
       {
         "week": "W2",
         "value": 52
       },
       {
         "week": "W3",
         "value": 49
       }
     ]
   },
   "spec": {
     "series": [
       {
         "type": "line",
-        "smooth": true
+        "smooth": true,
+        "lineStyle": {
+          "width": 4
+        }
       }
-    ]
+    ],
+    "palette": "viridis",
+    "label": {
+      "show": true,
+      "derive": "deltaPrev"
+    }
   }
 }

Full spec

{
  "type": "chart:line:smooth",
  "data": {
    "rows": [
      {
        "week": "W1",
        "value": 40
      },
      {
        "week": "W2",
        "value": 52
      },
      {
        "week": "W3",
        "value": 49
      }
    ]
  },
  "spec": {
    "series": [
      {
        "type": "line",
        "smooth": true,
        "lineStyle": {
          "width": 4
        }
      }
    ],
    "palette": "viridis",
    "label": {
      "show": true,
      "derive": "deltaPrev"
    }
  }
}

Everything you can set

Control	Layer	Where it lands
Data
Chart type	Core	`type`
Series type	Core	`type`
Category column	Core	`spec.categoryField`
Measure column	Core	`spec.series[]`
Style
Series colors	Core	`overrides.chart.series.1`
Smooth line	ECharts	`spec.series[].smooth`
Line width	ECharts	`spec.series[].lineStyle.width`
Color scheme	Core	`spec.palette`
Conditional colors	Core	`spec.colorRules`
Labels
Show legend	ECharts	`spec.legend.show`
Legend position	ECharts	`spec.legend.position`
Show data labels	Core	`spec.label.show`
Label position	Core	`spec.label.position`
Format	Core	`spec.label.format`
Label value	Core	`spec.label.derive`
Rotate	Core	`spec.label.rotate`
Font size	Core	`spec.label.fontSize`
Label color	Core	`spec.label.color`
Tooltip	Core	`spec.tooltip`
Axes
X-axis name	Core	`spec.xAxis.name`
Y-axis name	Core	`spec.yAxis.name`
Y-axis min	Core	`spec.yAxis.min`
Y-axis max	Core	`spec.yAxis.max`
Y-axis scale	Core	`spec.yAxis.type`
X-axis label rotate	Core	`spec.xAxis.axisLabel.rotate`
X-axis label size	Core	`spec.xAxis.axisLabel.fontSize`
Y-axis label size	Core	`spec.yAxis.axisLabel.fontSize`
X-axis label spacing	Core	`spec.xAxis.axisLabel.margin`
X-axis format	Core	`spec.xAxis.axisLabel.format`
Y-axis format	Core	`spec.yAxis.axisLabel.format`
X-axis gridlines	Core	`spec.gridlines.x.show`
Y-axis gridlines	Core	`spec.gridlines.y.show`
Plot density	Core	`spec.density`
Advanced
Boundary gap	Core	`spec.xAxis.boundaryGap`
Annotations	Core	`spec.annotations`

Chart spec fields

Every chart type accepts these ChartSpec fields. Most are dvt spec fields the renderer compiles for you. grid passes straight through to ECharts; series mixes ECharts series options with dvt's dataField; and any key on xAxis, yAxis, legend, or tooltip that is not a documented dvt key passes through too.

Field	What it does
`xAxis`	One axis, or an array of axes, via `AxisSpec`: type, name, min, max, scale, log, and label formatting.
`yAxis`	Same shape as `xAxis`, for the value axis: type, name, min, max, scale, log, and label formatting.
`series`	Per-series overrides: `type`, `dataField`, `name`, `stack`, `smooth`, `itemStyle`, `lineStyle`, `areaStyle`, `label`.
`legend`	Show or hide the legend, set its position, and format an aggregated value shown next to each entry.
`tooltip`	Choose which fields appear, a totals row, field order, a custom template, and crosshair behavior.
`grid`	A raw ECharts grid box (`left`, `right`, `top`, `bottom`, `containLabel`), passed through unmodified.
`funnelRate`	Show a conversion-rate label on a funnel: `step`, `overall`, `total`, or `none`, with a `precision`.
`label`	Data labels: `show`, `position`, `format`, a derived value (percent of total, delta), rotation, size, color.
`gridlines`	Toggle and style gridlines per axis: `show`, dashed or solid `style`, `width`, and `color`.
`banding`	Alternating background bands along one axis, to make long rows or columns easier to scan.
`plotArea`	Set the plot area's background fill and border color.
`gridPadding`	Explicit `left`, `right`, `top`, and `bottom` padding around the plot area, each a number or a string.
`density`	Overall plot density: `comfortable` (default spacing) or `compact` (tighter margins).
`palette`	Name a registered color scheme to apply to the series, instead of the default categorical colors.
`categoryColors`	Map specific category values to explicit colors, overriding the palette for just those categories.
`colorRules`	Apply a color to a data point the first time one of its ordered `when` conditions matches.
`colorScale`	A continuous color scale (`sequential`, `diverging`, or `piecewise`) with a scheme, domain, and buckets.
`annotations`	Fixed or computed reference lines, bands, points, or text, placed at an axis value or a stat of a field.
`trendline`	Overlay a fitted trend line: `true` for a default linear fit, or an object naming the method and order.
`footnotes`	Up to 50 footnote entries, each a marker plus explanatory text, rendered below the chart.
`sourceNote`	A single line of source-attribution text rendered below the chart.

Build it in dvt

Every chart type on this site is a few lines of the same declarative JSON spec. Read the full spec format, or connect an AI agent to your warehouse and build one live in the quickstart.

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