apply

Difference between using a spread syntax (…) and push.apply, when dealing with arrays

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Both Function.prototype.apply and the spread syntax may cause a stack overflow when applied to large arrays: let xs = new Array(500000), ys = [], zs; xs.fill(“foo”); try { ys.push.apply(ys, xs); } catch (e) { console.log(“apply:”, e.message) } try { ys.push(…xs); } catch (e) { console.log(“spread:”, e.message) } zs = ys.concat(xs); console.log(“concat:”, zs.length) Use Array.prototype.concat instead. … Read more

Including the group name in the apply function pandas python

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I think you should be able to use the nameattribute: temp_dataframe.groupby(level=0,axis=0).apply(lambda x: foo(x.name, x)) should work, example: In [132]: df = pd.DataFrame({‘a’:list(‘aabccc’), ‘b’:np.arange(6)}) df Out[132]: a b 0 a 0 1 a 1 2 b 2 3 c 3 4 c 4 5 c 5 In [134]: df.groupby(‘a’).apply(lambda x: print(‘name:’, x.name, ‘\nsubdf:’,x)) name: a subdf: … Read more

Why does pandas apply calculate twice

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This behavior is intended, as an optimization. See the docs: In the current implementation apply calls func twice on the first column/row to decide whether it can take a fast or slow code path. This can lead to unexpected behavior if func has side-effects, as they will take effect twice for the first column/row.

How do I wrap a function in Javascript?

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Personally instead of polluting builtin objects I would go with a decorator technique: var makeSafe = function(fn){ return function(){ try{ return fn.apply(this, arguments); }catch(ex){ ErrorHandler.Exception(ex); } }; }; You can use it like that: function fnOriginal(a){ console.log(1/a); }; var fn2 = makeSafe(fnOriginal); fn2(1); fn2(0); fn2(“abracadabra!”); var obj = { method1: function(x){ /* do something */ … Read more

Apply function on each row (row-wise) of a NumPy array

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You can use np.apply_along_axis: np.apply_along_axis(function, 1, array) The first argument is the function, the second argument is the axis along which the function is to be applied. In your case, it is the first axis. The last argument is the array, of course. You should be warned, however, that apply_along_axis is only a convenience function, … Read more

Create new column based on values from other columns / apply a function of multiple columns, row-wise in Pandas

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OK, two steps to this – first is to write a function that does the translation you want – I’ve put an example together based on your pseudo-code: def label_race (row): if row[‘eri_hispanic’] == 1 : return ‘Hispanic’ if row[‘eri_afr_amer’] + row[‘eri_asian’] + row[‘eri_hawaiian’] + row[‘eri_nat_amer’] + row[‘eri_white’] > 1 : return ‘Two Or More’ … Read more

In Javascript is there equivalent to .apply that doesn’t change the value of this?

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You cannot, because of the way this works in JavaScript. Read on: Going by the “Entering An Execution Context” section of the ECMAScript spec: when you call a function, the value of this is determined by what’s to it’s left (called the activation object) . Let’s create a function called steve, and put him in … Read more

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