Here is a small example of how it could be done using for loops with the mtcars dataset for(g in unique(mtcars$gear)) { f <- filter(mtcars, gear == g) p <- ggplot(f, aes(disp, hp)) + geom_point() ggsave(paste0(‘plot_’, g,’.jpg’), p) } In your case it would something like this for(s in unique(WQ_byStation$StationName)){ f <- filter(WQ_byStation, StationName == … Read more
TL;DR Your best bets are usually a for-of loop (ES2015+ only; spec | MDN) – simple and async-friendly for (const element of theArray) { // …use `element`… } forEach (ES5+ only; spec | MDN) (or its relatives some and such) – not async-friendly (but see details) theArray.forEach(element => { // …use `element`… }); a simple … Read more
If you want to divide a list into slices you can use this trick: list_of_slices = zip(*(iter(the_list),) * slice_size) For example >>> zip(*(iter(range(10)),) * 3) [(0, 1, 2), (3, 4, 5), (6, 7, 8)] If the number of items is not dividable by the slice size and you want to pad the list with None … Read more
This is one of the gotchas! of python, that can escape beginners. The words[:] is the magic sauce here. Observe: >>> words = [‘cat’, ‘window’, ‘defenestrate’] >>> words2 = words[:] >>> words2.insert(0, ‘hello’) >>> words2 [‘hello’, ‘cat’, ‘window’, ‘defenestrate’] >>> words [‘cat’, ‘window’, ‘defenestrate’] And now without the [:]: >>> words = [‘cat’, ‘window’, ‘defenestrate’] … Read more
Why don’t you just do it the idiomatic C way? This ought to be bullet-proof, but it won’t be fast. I’m pretty sure indexing into a list in Python walks the linked list, so this is a “Shlemiel the Painter” algorithm. But I tend not to worry about optimization until it becomes clear that a … Read more
Try this: [(i, j) for i, j in enumerate(mylist)] You need to put i,j inside a tuple for the list comprehension to work. Alternatively, given that enumerate() already returns a tuple, you can return it directly without unpacking it first: [pair for pair in enumerate(mylist)] Either way, the result that gets returned is as expected: … Read more
Use children() and each(), you can optionally pass a selector to children $(‘#mydiv’).children(‘input’).each(function () { alert(this.value); // “this” is the current element in the loop }); You could also just use the immediate child selector: $(‘#mydiv > input’).each(function () { /* … */ });
Using a helper function (originally defined at Converting a C-style for loop that uses division for the step to Swift 3) public func sequence<T>(first: T, while condition: @escaping (T)-> Bool, next: @escaping (T) -> T) -> UnfoldSequence<T, T> { let nextState = { (state: inout T) -> T? in // Return `nil` if condition is … Read more
If you’re looping through an array, it shouldn’t matter – the enhanced for loop uses array accesses anyway. For example, consider this code: public static void main(String[] args) { for (String x : args) { System.out.println(x); } } When decompiled with javap -c Test we get (for the main method): public static void main(java.lang.String[]); Code: … Read more
You want: for (i = 0; i < strlen(source); i++) { sizeof gives you the size of the pointer, not the string. However, it would have worked if you had declared the pointer as an array: char source[] = “This is an example.”; but if you pass the array to function, that too will decay … Read more