DataFrame.apply
Apply a function to each element or along a specified axis of a DataFrame. Supports JavaScipt functions when axis is not specified, and accepts Tensorflow functions when axis is specified.
danfo.DataFrame.apply(kwargs) [source]
Parameters | Type | Description | Default |
kwargs | Object | {callable: Function to call on each element, axis: undefined: if undefined, then any JavaScript function is accepted and will be applied element-wise. 0: Apply along row/index axis 1: Apply across columns axis } | undefined |
Returns:
return DataFrame
The apply function calls a JavaScript function on every element of the DataFrame when the axis is not specified.
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const dfd = require("danfojs-node")let data = [[1, 2, 3], [4, 5, 6], [20, 30, 40], [39, 89, 78]]let cols = ["A", "B", "C"]let df = new dfd.DataFrame(data, { columns: cols })function sum_vals(x) {return x + 20}let df_new = df.apply({callable: sum_vals })df_new.print()
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╔═══╤═══════════════════╤═══════════════════╤═══════════════════╗║ │ A │ B │ C ║╟───┼───────────────────┼───────────────────┼───────────────────╢║ 0 │ 21 │ 22 │ 23 ║╟───┼───────────────────┼───────────────────┼───────────────────╢║ 1 │ 24 │ 25 │ 26 ║╟───┼───────────────────┼───────────────────┼───────────────────╢║ 2 │ 40 │ 50 │ 60 ║╟───┼───────────────────┼───────────────────┼───────────────────╢║ 3 │ 59 │ 109 │ 98 ║╚═══╧═══════════════════╧═══════════════════╧═══════════════════╝
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const dfd = require("danfojs-node")let data = [{ short_name: ["NG", "GH", "EGY", "SA"] },{ long_name: ["Nigeria", "Ghana", "Eqypt", "South Africa"] }]let df = new dfd.DataFrame(data)function lower(x) {return `${x}`.toLowerCase()}let df_new = df.apply({ callable: lower })df_new.print()
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╔═══╤═══════════════════╤═══════════════════╗║ │ short_name │ long_name ║╟───┼───────────────────┼───────────────────╢║ 0 │ ng │ nigeria ║╟───┼───────────────────┼───────────────────╢║ 1 │ gh │ ghana ║╟───┼───────────────────┼───────────────────╢║ 2 │ egy │ eqypt ║╟───┼───────────────────┼───────────────────╢║ 3 │ sa │ south africa ║╚═══╧═══════════════════╧═══════════════════╝
Apply Tensorflow function element-wise
You can call any compatible Tensorflow function on a DataFrame across a specified axis. For functions that operate element-wise and returns the same shape as the original DataFrame, you must specify an axis of 0.
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const dfd = require("danfojs-node")let data = [[1, 2, 3], [4, 5, 6], [20, 30, 40], [39, 89, 78]]let cols = ["A", "B", "C"]let df = new dfd.DataFrame(data, { columns: cols })function sum_vals(x) {return x.logSigmoid()}let df_new = df.apply({axis: 0, callable: sum_vals })df_new.print()
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╔═══╤═══════════════════╤═══════════════════╤═══════════════════╗║ │ A │ B │ C ║╟───┼───────────────────┼───────────────────┼───────────────────╢║ 0 │ -0.3132616579... │ -0.1269280463... │ -0.0485873296... ║╟───┼───────────────────┼───────────────────┼───────────────────╢║ 1 │ -0.0181499607... │ -0.0067153489... │ -0.0024756519... ║╟───┼───────────────────┼───────────────────┼───────────────────╢║ 2 │ -2.0611536921... │ -9.3576229122... │ -4.2483541311... ║╟───┼───────────────────┼───────────────────┼───────────────────╢║ 3 │ -1.1548223864... │ -2.2273639090... │ -1.3336148713... ║╚═══╧═══════════════════╧═══════════════════╧═══════════════════╝
Apply Tensorflow function along column axis
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const dfd = require("danfojs-node")let data = [[1, 2, 3], [4, 5, 6], [20, 30, 40], [39, 89, 78]]let cols = ["A", "B", "C"]let df = new dfd.DataFrame(data, { columns: cols })function sum_vals(x) {return x.sum()}let df_new = df.apply({axis: 1, callable: sum_vals })df_new.print()
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╔═══╤══════════════════════╗║ │ 0 ║╟───┼──────────────────────╢║ A │ 64 ║╟───┼──────────────────────╢║ B │ 126 ║╟───┼──────────────────────╢║ C │ 127 ║╚═══╧══════════════════════╝
Last updated 5 months ago