forked from sheetjs/sheetjs
80 lines
2.9 KiB
Markdown
80 lines
2.9 KiB
Markdown
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#### Formulae
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The A1-style formula string is stored in the `f` field. Even though different
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file formats store the formulae in different ways, the formats are translated.
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Even though some formats store formulae with a leading equal sign, CSF formulae
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do not start with `=`.
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The worksheet representation of A1=1, A2=2, A3=A1+A2:
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```js
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{
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"!ref": "A1:A3",
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A1: { t:'n', v:1 },
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A2: { t:'n', v:2 },
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A3: { t:'n', v:3, f:'A1+A2' }
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}
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```
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Shared formulae are decompressed and each cell has the formula corresponding to
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its cell. Writers generally do not attempt to generate shared formulae.
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Cells with formula entries but no value will be serialized in a way that Excel
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and other spreadsheet tools will recognize. This library will not automatically
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compute formula results! For example, to compute `BESSELJ` in a worksheet:
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```js
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{
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"!ref": "A1:A3",
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A1: { t:'n', v:3.14159 },
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A2: { t:'n', v:2 },
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A3: { t:'n', f:'BESSELJ(A1,A2)' }
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}
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```
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**Array Formulae**
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Array formulae are stored in the top-left cell of the array block. All cells
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of an array formula have a `F` field corresponding to the range. A single-cell
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formula can be distinguished from a plain formula by the presence of `F` field.
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For example, setting the cell `C1` to the array formula `{=SUM(A1:A3*B1:B3)}`:
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```js
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worksheet['C1'] = { t:'n', f: "SUM(A1:A3*B1:B3)", F:"C1:C1" };
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```
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For a multi-cell array formula, every cell has the same array range but only the
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first cell has content. Consider `D1:D3=A1:A3*B1:B3`:
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```js
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worksheet['D1'] = { t:'n', F:"D1:D3", f:"A1:A3*B1:B3" };
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worksheet['D2'] = { t:'n', F:"D1:D3" };
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worksheet['D3'] = { t:'n', F:"D1:D3" };
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```
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Utilities and writers are expected to check for the presence of a `F` field and
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ignore any possible formula element `f` in cells other than the starting cell.
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They are not expected to perform validation of the formulae!
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**Formula Output**
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The `sheet_to_formulae` method generates one line per formula or array formula.
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Array formulae are rendered in the form `range=formula` while plain cells are
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rendered in the form `cell=formula or value`. Note that string literals are
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prefixed with an apostrophe `'`, consistent with Excel's formula bar display.
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**Formulae File Format Details**
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| Storage Representation | Formats | Read | Write |
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|:-----------------------|:-------------------------|:-----:|:-----:|
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| A1-style strings | XLSX | :o: | :o: |
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| RC-style strings | XLML and plaintext | :o: | :o: |
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| BIFF Parsed formulae | XLSB and all XLS formats | :o: | |
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| OpenFormula formulae | ODS/FODS/UOS | :o: | :o: |
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Since Excel prohibits named cells from colliding with names of A1 or RC style
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cell references, a (not-so-simple) regex conversion is possible. BIFF Parsed
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formulae have to be explicitly unwound. OpenFormula formulae can be converted
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with regexes for the most part.
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