ihb2032/MoonFrame/chart

README
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CellParseLocation
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ChartKind
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ChartSpec
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ClosedInterval
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CsvReadOptions
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CsvWriteOptions
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DataError
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DataFrame
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DataType
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Expr
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Field
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HtmlOptions
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JoinOptions
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JoinType
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JsonReadOptions
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KeepStrategy
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LazyFrame
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OnParseError
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ParseErrorDetail
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Scalar
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Schema
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Series
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TypeMismatchDetail
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VegaType
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col
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cols
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format_vega_lite
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lit
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lit_bool
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lit_float
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lit_int
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lit_series
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lit_str
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map_many
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read_csv
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read_json
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read_ndjson
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scan_csv
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scan_ndjson
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when
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write_csv
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write_json
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write_ndjson
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write_vega_lite

ihb2032/MoonFrame/chart does not have a README file

ChartKind

pub(all) enum ChartKind {
  Bar
  Line
  Point
  Area
} derive(Eq, @moonbitlang/core/debug.Debug
Debug)

The mark type of a chart, mapped to a Vega-Lite top-level mark: Bar → "bar", Line → "line", Point → "point", Area → "area". pub(all) so callers can name the variants when building a ChartSpec (though the ChartSpec::bar / line / point / area constructors set the kind for you).

ChartKind::equal

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fn ChartKind::equal(ChartKind, ChartKind) -> Bool

ChartKind::not_equal

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fn ChartKind::not_equal(x : ChartKind, y : ChartKind) -> Bool

ChartKind::to_repr

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fn ChartKind::to_repr(ChartKind) -> @moonbitlang/core/debug.Repr
Repr

ChartSpec

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pub struct ChartSpec {
  kind : ChartKind
  x : String
  y : String
  color : String?
  title : String?
  color_type : VegaType?
} derive(Eq, @moonbitlang/core/debug.Debug
Debug)

A chart specification: the mark kind, the x / y encoding columns, an optional color grouping column, and an optional title. Fields are read-only outside the package — build a spec through one of the mark-named constructors (ChartSpec::bar(x, y) / line / point / area), naming color / color_type / title as needed:

ChartSpec::bar("region", "revenue", title="Revenue by region")

x / y / color are column names resolved against the frame at format_vega_lite time (a missing name raises ColumnNotFound); each column's dtype decides its Vega-Lite field type — the rule format_vega_lite's doc states (numeric → quantitative, Date → temporal, otherwise → nominal) — unless color_type overrides the color channel: e.g. a numeric grouping column (a cluster id) rendered as Nominal distinct colors rather than a continuous gradient (only color honours an override; x / y keep dtype inference).

ChartSpec::area

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fn ChartSpec::area(x : String, y : String, color? : String, color_type? : VegaType, title? : String) -> ChartSpec

An area chart of y against x (Vega-Lite mark: "area").

The optional color / color_type / title parameters carry the ChartSpec doc's colour-encoding and title contract (only color honours a color_type override; x / y keep dtype inference).

ChartSpec::bar

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fn ChartSpec::bar(x : String, y : String, color? : String, color_type? : VegaType, title? : String) -> ChartSpec

A bar chart of y against x (Vega-Lite mark: "bar").

The optional color / color_type / title parameters carry the ChartSpec doc's colour-encoding and title contract (only color honours a color_type override; x / y keep dtype inference).

ChartSpec::equal

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fn ChartSpec::equal(ChartSpec, ChartSpec) -> Bool

ChartSpec::line

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fn ChartSpec::line(x : String, y : String, color? : String, color_type? : VegaType, title? : String) -> ChartSpec

A line chart of y against x (Vega-Lite mark: "line").

The optional color / color_type / title parameters carry the ChartSpec doc's colour-encoding and title contract (only color honours a color_type override; x / y keep dtype inference).

ChartSpec::not_equal

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fn ChartSpec::not_equal(x : ChartSpec, y : ChartSpec) -> Bool

ChartSpec::point

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fn ChartSpec::point(x : String, y : String, color? : String, color_type? : VegaType, title? : String) -> ChartSpec

A scatter (point) chart of y against x (Vega-Lite mark: "point").

The optional color / color_type / title parameters carry the ChartSpec doc's colour-encoding and title contract (only color honours a color_type override; x / y keep dtype inference).

ChartSpec::to_repr

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fn ChartSpec::to_repr(ChartSpec) -> @moonbitlang/core/debug.Repr
Repr

VegaType

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pub(all) enum VegaType {
  Quantitative
  Nominal
  Ordinal
  Temporal
} derive(Eq, @moonbitlang/core/debug.Debug
Debug)

A Vega-Lite field type, used to override the dtype-based inference for the color channel. pub(all) so callers can name the variants in a constructor's color_type. Quantitative is a continuous measure (a color gradient), Nominal an unordered category (distinct colors per value), Ordinal an ordered category, and Temporal a time field.

VegaType::equal

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fn VegaType::equal(VegaType, VegaType) -> Bool

VegaType::not_equal

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fn VegaType::not_equal(x : VegaType, y : VegaType) -> Bool

VegaType::to_repr

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fn VegaType::to_repr(VegaType) -> @moonbitlang/core/debug.Repr
Repr

format_vega_lite

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fn format_vega_lite(df : @ihb2032/MoonFrame/frame.DataFrame
DataFrame, spec : ChartSpec) -> String raise @ihb2032/MoonFrame/types.DataError
DataError

Render df and spec as a complete Vega-Lite v5 specification JSON string: $schema (pinned to the Vega-Lite v5 schema URL) + optional title + mark (from spec.kind) + encoding (x / y and, when set, color, each {field, type}) + data.values (the frame inlined as JSON records, sharing format_json's cell mapping — null and non-finite-float cells become JSON null). A frame with the encoded columns but zero rows yields "data":{"values":[]}.

Each encoding channel's field type follows its column's dtype — the single statement of the dtype→type rule: a numeric column (Int / Float) is "quantitative", a Date column is "temporal" (its ISO cells — data.values' date units, via the JSON records' ISO mapping — sort chronologically), and every other dtype is "nominal" — unless the channel carries an explicit color_type override.

The spec's x / y / color columns are resolved left-to-right; the first name absent from df raises ColumnNotFound(name) — this is the one reason the function is not total (it accepts column names, and a name can be wrong). The emitted text is always valid JSON (it is built through @json and stringified), so it round-trips through any standards-compliant JSON / Vega-Lite reader.

write_vega_lite

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fn write_vega_lite(path : String, df : @ihb2032/MoonFrame/frame.DataFrame
DataFrame, spec : ChartSpec) -> Unit raise @ihb2032/MoonFrame/types.DataError
DataError

Write a Vega-Lite v5 spec for df / spec to path. Mirrors write_json: a ColumnNotFound from format_vega_lite (a spec column absent from df) propagates unchanged, a filesystem failure surfaces as raise IoError(message), and content holding an unpaired UTF-16 surrogate is refused with raise InvalidOperation.