I have a nested array, like this:
aux = [["None", ""],["Average", "avg"],["Summation", "sum"],["Maximum", "max"],["Minimum", "min"],["Count", "count"],["Distinct Count", "distinctCount"],["Max Forever", "maxForever"],["Min Forever","minForever"],["Standard Deviation","stddev"]]
Now, what i want to do, is to append "1234" (it's an example) to the beginning of the second element of each array, but not on the original array, like this:
new_aux = aux.map {|k| [k[0],k[1].prepend("1234")]}
Problem is that with this, the original array is being changed. I was reading about this and the problem seems to be the manipulation of the string, because if i convert that element to symbol, for example, the original array its not changed, like i want, but i don't exactly get what is the problem here and how should i do this.
By doing this, in new_aux i get:
[["None", "1234"],
["Average", "1234avg"],
["Summation", "1234sum"],
["Maximum", "1234max"],
["Minimum", "1234min"],
["Count", "1234count"],
["Distinct Count", "1234distinctCount"],
["Max Forever", "1234maxForever"],
["Min Forever", "1234minForever"],
["Standard Deviation", "1234stddev"]]
Which is what i want, the thing is that i have the exact same thing in the original array, which is what i don't want.
prepend mutates a string itself, so using this method you change the source array. Use strings interpolation to achieve your goal new_aux = aux.map {|k| [k[0],"1234#{k[1]}"]}
Related
As part of my nightwatchjs testing script, I have a 'dynamic' array that I would like to add a character to.
So, at the moment my array has a value of 4000, but I would like this to read 4,000.
This means that I need to add a , to my array.
The issue I have however, is that this value could change the next time I run the test script, so it could be 10000 or 100000.
So I suppose what I'm asking is whether it's possible to "select a value 3 elements from the end of my array?"
So no matter what or how many elements are in the array, the array will read xx,000.
Any help would be much appreciated. Many thanks.
Does this array have a single value? If so, why is it an array instead of just a variable?
You can use toLocaleString() to add commas to a numeric value, but it will return a string and not a number.
let arr = [4000]
let num = arr[0]
let commas = num.toLocaleString()
console.log(commas)
// "4,000"
I have a small problem. I created a large array.
It looks like this:
var Array = [
["text10", "text11", ["text01", "text02"]],
["text20", "text21", ["text11", "text12"]]
]
If we write this way: Array[0] that shows all the elements.
If we write this way: Array[0][0] that shows "text1".
If we write this way: Array[0][2] that shows
-2 elements
-- 0: "text01"
-- 1: "text02"
.
If we write this way: Array[0][2].count or Array[0][2][0] it will not work
How do I choose each item, I need these elements for the tableView
The problem basically is that your inner array is illegal. Swift arrays must consist of elements of a single type. You have two types of element, String and Array Of String. Swift tries to compensate but the result is that double indexing can’t work, not least because there is no way to know whether a particular element will have a String or an Array in it.
The solution is to rearchitect completely. If your array entries all consist of the same pattern String plus String plus Array of String, then the pattern tells you what to do; that should be a custom struct, not an array at all.
as #matt already answered but I want to add this thing
Why Array[0][2].count or Array[0][2][0] not work
If you Define array
var array = [
["text10", "text11", ["text01", "text02"]],
["text20", "text21", ["text11", "text12"]]
]
And when you type array you can see it's type is [[Any]] However it contains String as well as Array
So When you try to get Array[0][2] Swift does not know that your array at position 2 has another array which can have count
EDIT
What you are asking now is Array of dictionary I suggest you to go with model i.e create struct or class and use it instead of dictionary
Now If you want to create dictionary then
var arrOfDict = ["text10" : ["text01", "text02"] , "text11" : ["text11", "text12"]]
And you can access with key name let arrayatZero = arrOfDict["text10"] as? [String]
I have an array like this I use
inputx.scan(/.*?\n/)
for create array this is a representation of my array
element 1 => [car;dog;soda]
element 2 => [bunny;pc;laptop]
element 3 => [hand;sword;shield]
this is my text file I use scan method for create array inputx.scan(/.*?\n/)
car;dog;soda
bunny;pc;laptop
hand;sword;shield
I need to replace each comma by number of array for obtain this
this is my expected output
in this output I replace ";" by "nthelementnumber;" example 1;
car1;dog1;soda
bunny2;pc2;laptop
hand3;sword3;shield
Please help me
It's a bit hard to tell what exactly your array looks like, but I'm going to take a guess:
element = ['car;dog;soda',
'bunny;pc;laptop',
'hand;sword;shield']
If that's correct, you can get the output you are looking for with something like:
element.each_index {|i| element[i] = element[i].gsub(';', "#{i+1};")}
The each_index iterator gives you each index (unsurprisingly). Then you can use each index to manipulate each value in the array.
I'm a total Perl newb, but still cannot believe I cannot figure this out with all the info I've read through online, but, I've burned too much time and am suffering from block at this point. Hoping to learn something based on my real life example...
Ok, I think I have an array of arrays, created like this:
my #array1 = ();
my #array2 = ();
my $ctr1 = 0;
my $col;
[sql query]
while(($col)=$sth->fetchrow_array() ) {
$array1[$ctr1]=$col;
$ctr1++;
}
print STDERR "#array1";
##results in 10 rows, a mac address in each
##00:00:00:00:00:00 00:11:11:11:11:11 22:22:22:22:22:22 33:33:33:33:33:33 ...
Now I do another query. While looping through results, I am looking for those 10 mac addresses. When I find one, I add a row to array2 with the mac and the sequential number accumulated to the point, like this:
[sql query]
while(($col)=$sth->fetchrow_array() ) {
$ctr2++;
if( my ($matched) = grep $_ eq $col, #array1 ) {
push( #array2, ($col,$ctr2) );
}
}
print STDERR "#array2";
##results in 10 rows, a mac address and an integer in each
##00:00:00:00:00:00 2 00:11:11:11:11:11 24 22:22:22:22:22:22 69 33:33:33:33:33:33 82 ...
Now the easy part. I want to loop through array2, grabbing the mac address to use as part of a sql query. Therein lies the problem. I am so ignorant as to exactly what I am doing that even though I had it almost working, I can't get back to that point. Ignorance is definitely not bliss.
When I loop through array2, I am getting a host of errors, based on the different forms of the statement. The one I think is right is listed below along with the error message...
my $ctr3 = 0;
foreach $ctr3 (#array2) {
my $chkmac = $array2[$ctr3][0]; <--- gacks here with the error below - line 607
[SQL query]
[Thu May 30 14:05:09 2013] [error] Can't use string ("00:66:55:77:99:88") as an ARRAY ref while "strict refs" in use at /path/to/test.cgi line 607.\n
I believe the issue is that my array of arrays is not an array of arrays. If it were, it would work as coded, or so I think from the reading... That said, I cannot fathom what I am dealing with otherwise. This will be a head slapper I'm all but sure, but I am stumped.... Little help, please?
TIA
O
For an array of arrays you want to use an array reference, e.g.
push #array2, [$col, $ctr2];
When accessing an element within an array refernce, you'll want to use the -> operator. Also, when looping through an array, it's not necessary to index back into that same array. So the last part would look more like:
foreach $ctr3 (#array2) {
my $chkmac = $ctr3->[0];
....
When you do the foreach there, $ctrl3 won't have the index in it, it'll have the value. So you should just need to do $ctrl3->[0]. Note the -> which dereferences the array reference (#array2 is actually an array of array references).
EDIT: As AKHolland pointed out, #array2 actually isn't an array of array references, although that's what it should be. You also need to change:
push( #array2, ($col, $ctr2) );
To
push( #array2, [$col, $ctr2] );
This makes an array reference, rather than a list. A list in this context just collapses down into regular arguments to push, meaning you're pushing two separate strings into #array2.
You are correct that your array of arrays is not an array of arrays, since in Perl there is no such thing. So what do you have instead? There's two ways to see.
First, when you print #array2, you come up with a string composed of alternating MACs and counts, separated by spaces. Since the spaces sort-of-signify the division between array elements, we might surmise that what we've got is a single array of heterogeneous elements, such that element 0 is a MAC, element 1 is a count, element 2 is another MAC, and so on.
The other perspective is to look at how #array2 is constructed:
push( #array2, ($col,$ctr2) );
From the documentation for push, we find that push ARRAY LIST works by appending the elements of LIST to the end of ARRAY. This has the effect of flattening the list into the array such that its original identity as a list is lost. You can add all the parentheses you want, when Perl expects a list it flattens all of them away.
So how do you achieve the effect you want? The List-of-Lists documentation has a detailed treatment, but the short answer is that you make a list of array references. Array references are scalars and are therefore legal elements in an array. But they retain their identify as array references!
The anonymous array reference constructor is the square bracket []. In order to push an array reference containing the elements $col and $ctr2 onto the end of #array2, you simply do this:
push( #array2, [$col, $ctr2] );
The code you wrote for accessing a particular element of the array-reference-in-an-array now works. But since I've already written a bunch of paragraphs on the subject, let me finish by explaining what was wrong originally and how changing the push statements suddenly makes it work.
The expression $array2[$ctr3][0] is sometimes written as $array2[$ctr3]->[0] to clarify what it's actually doing. What it does is to take the value of $array2[$ctr3] and treat it as an array reference, taking its 0 element. If we take $ctr3 to be 0 (as it would be at the top of the loop) the value of $array2[$ctr3] is the first element, 00:00:00:00:00:00. When you then subsequently ask Perl to treat 00:00:00:00:00:00 as an array reference, Perl dies because it doesn't know how to treat a string as an array reference.
When instead the value of $array2[$ctr3] is an array reference because that is what you pushed onto #array2 when constructing it, Perl is able to do as you ask, dereferencing the array reference and looking at element 0 of the resulting array, whose value happens to be 00:00:00:00:00:00.
So, what I am trying to do is create a variable that holds 50 lists/arrays. Accessing an element in this variable would return one of the lists. If there are no elements at a given index, I would like it to return [].
My logic to initialize this would be something like:
spectrum_map=[];
for n=1:spectrum_blocks
spectrum_map=[spectrum_map,[]];
end
However, after doing so, I simply get an empty matrix:
spectrum_map =
[]
What I want to see is something like:
spectrum_map =
[] [] [] [] [] ....
That way, if I were to access spectrum_map(2), I would see that it is empty. However, instead I would get an error that the index exceeds matrix dimensions.
Is there some other way to do what I am trying to achieve?
You can get the effect you're looking for if you use a cell array instead of a matrix.
spectrum_map = cell( 1, 50 );
spectrum_map{50}
ans =
[]
If you need to convert back to a matrix later (to perform some math on it, for instance) you can use the cell2mat function.