I try to draw a graph from tens of thousands points, but because this number is so big i need to reduce it. Many of them have duplicates. I tried to reduce the number using this:
var array=_.reject(data,function(object,i){
return i>0 && (data[i-1].a === object.a && data[i-1].b===object.b && data[i-1].c===object.c);
});
How can i modify this function, or to create a new one, in order to keep first and last value considered duplicate. Those are different by another attribute 'd' which represent a time stamp.
//return filtered points, compareFunction for sorting, equalFunction for
//removing points
function removeDuplicate(data,compareFunction,equalFunction) {
data.sort(function(pointa, pointb) {
var compare = compareFunction(pointa,pointb);
return compare;
});
var arr = new Array();
var prev = new Object();
var index = 0;
for (var i = 0; i < data.length; i++) {
if (i == 0 || !(equalFunction(prev,data[i]))) {
arr[index++] = data[i];
prev = data[i];
}
}
return arr;
}
function compareFunction(pointa,pointb){
return (pointa.a + pointa.b + pointa.c) - (pointb.a + pointb.b + pointb.c);
}
function equalFunction(pointa,pointb){
return pointa.a == pointb.a && pointa.b == pointb.b && pointa.c == pointb.c;
}
example - https://jsfiddle.net/8xu4Lwp2/
The simplest way to eliminate duplicates from an array in JavaScript is to cast it as a Set and then back to an Array. Sets don't store duplicates.
// not sure why setArr isn't logging, it does in Opera console.
arr=[1,1,2,2,3,3];
console.log(arr);
setArr=new Set(arr);
console.log(setArr);
newArr=[...setArr];
console.log(newArr);
Cool solution:
var unique = Array.from(new Set(arrayWithDuplicatedValue));
I've a strange thing to do but I don't know how to start
I start with this vars
var base = [1,1,1,2,3,5,7,9,14,19,28,40,56,114,232,330];
var sky = [0,0,0,3,4,5,6,7,8,9,10,11,12,14,16,17];
var ite = [64,52,23,38,13,15,6,4,6,3,2,1,2,1,1,1];
So to start all the 3 array have the same length and the very first operation is to see if there is a duplicate value in sky array, in this case the 0 is duplicated and only in this case is at the end, but all of time the sky array is sorted. So I've to remove all the duplicate (in this case 0) from sky and remove the corresponding items from base and sum the corresponding items on ite. So if there's duplicate on position 4,5 I've to manipulate this conditions. But let see the new 3 array:
var new_base = [1,2,3,5,7,9,14,19,28,40,56,114,232,330];
var new_sky = [0,3,4,5,6,7,8,9,10,11,12,14,16,17];
var new_ite = [139,38,13,15,6,4,6,3,2,1,2,1,1,1];
If you see the new_ite have 139 instead the 64,52,23, that is the sum of 64+52+23, because the first 3 items on sky are the same (0) so I remove two corresponding value from base and sky too and I sum the corresponding value into the new_ite array.
There's a fast way to do that? I thought a for loops but I stuck at the very first for (i = 0; i < sky.length; i++) lol, cuz I've no idea on how to manipulate those 3 array in that way
J
When removing elements from an array during a loop, the trick is to start at the end and move to the front. It makes many things easier.
for( var i = sky.length-1; i>=0; i--) {
if (sky[i] == prev) {
// Remove previous index from base, sky
// See http://stackoverflow.com/questions/5767325/how-to-remove-a-particular-element-from-an-array-in-javascript
base.splice(i+1, 1);
sky.splice(i+1, 1);
// Do sum, then remove
ite[i] += ite[i+1];
ite.splice(i+1, 1);
}
prev = sky[i];
}
I won't speak to whether this is the "fastest", but it does work, and it's "fast" in terms of requiring little programmer time to write and understand. (Which is often the most important kind of fast.)
I would suggest this solution where j is used as index for the new arrays, and i for the original arrays:
var base = [1,1,1,2,3,5,7,9,14,19,28,40,56,114,232,330];
var sky = [0,0,0,3,4,5,6,7,8,9,10,11,12,14,16,17];
var ite = [64,52,23,38,13,15,6,4,6,3,2,1,2,1,1,1];
var new_base = [], new_sky = [], new_ite = [];
var j = -1;
sky.forEach(function (sk, i) {
if (!i || sk !== sky[i-1]) {
new_ite[++j] = 0;
new_base[j] = base[i];
new_sky[j] = sk;
}
new_ite[j] += ite[i];
});
console.log('new_base = ' + new_base);
console.log('new_sky = ' + new_sky);
console.log('new_ite = ' + new_ite);
You can use Array#reduce to create new arrays from the originals according to the rules:
var base = [1,1,1,2,3,5,7,9,14,19,28,40,56,114,232,330];
var sky = [0,0,0,3,4,5,6,7,8,9,10,11,12,14,16,17];
var ite = [64,52,23,38,13,15,6,4,6,3,2,1,2,1,1,1];
var result = sky.reduce(function(r, n, i) {
var last = r.sky.length - 1;
if(n === r.sky[last]) {
r.ite[last] += ite[i];
} else {
r.base.push(base[i]);
r.sky.push(n);
r.ite.push(ite[i]);
}
return r;
}, { base: [], sky: [], ite: [] });
console.log('new base:', result.base.join(','));
console.log('new sky:', result.sky.join(','));
console.log('new ite:', result.ite.join(','));
atltag's answer is fastest. Please see:
https://repl.it/FBpo/5
Just with a single .reduce() in O(n) time you can do as follows; (I have used array destructuring at the assignment part. One might choose to use three .push()s though)
var base = [1,1,1,2,3,5,7,9,14,19,28,40,56,114,232,330],
sky = [0,0,0,3,4,5,6,7,8,9,10,11,12,14,16,17],
ite = [64,52,23,38,13,15,6,4,6,3,2,1,2,1,1,1],
results = sky.reduce((r,c,i) => c === r[1][r[1].length-1] ? (r[2][r[2].length-1] += ite[i],r)
: ([r[0][r[0].length],r[1][r[1].length],r[2][r[2].length]] = [base[i],c,ite[i]],r),[[],[],[]]);
console.log(JSON.stringify(results));
I'm trying to find an index of a number in a 2d array, but console gives out
Uncaught TypeError: block[((a * 10) + c)].indexOf is not a function
I think it has something to do with the way of accessing the array element, but can't seem to find the problem.
Here's the code.
var block = [];
var temp;
var del;
for(var a = 0;a < 9;a++){
for(var b = 0;b < 9;b++){
temp = parseInt(prompt("enter element number " + b + " of row number " + a));
console.log(temp);
if(temp>0){
block[a*10+b] = temp;
}else{
block[a*10+b] = [1,2,3,4,5,6,7,8,9];
}
// console.log(block[a*10+b]);
}
}
for(var a = 0;a < 9;a++){
for(var b = 0;b < 9;b++){
if(typeof(block[a][b]) == "number"){
for(var c = 0;c < 9;c++){
if(c != b){
del = block[a*10+c].indexOf(b);
block[a*10+c].splice(del,1);
}
}
}
}
}
You have a mix of data types assigned to the block array. When the user enters a value that is not numeric, you assign indeed a nested array to one of the block elements, but not so when the user enters a valid number.
From what I think you are doing (a Sudoko game?) this might be intended: the numbers are known values in the grid, the nested arrays represent a list of values that are still possible at that particular cell.
But then in the second part of your code, you should check in which of the two cases you are, as you only want to remove array elements if the value you are looking at is indeed an array. This test you can do with Array.isArray().
There are also some other issues in the second part of your script:
The expression block[a][b] is not consistent with how you have filled that array: it should be block[a*10+b] to be consistent.
the b in .indexOf(b) is wrong: you are not looking for that value, but for block[a*10+b].
the splice() is always executed, even if the indexOf returned -1. This leads to an undesired effect, because if the first argument to splice() is negative, the index really is counted from the end of the array, and still an element is removed from the array. This should not happen: you should only execute the splice if the indexOf result is non-negative.
Below I have put a working version, but in order to avoid the almost endless prompts, I have provided this snippet with a textarea where you can input the complete 9x9 grid in one go, and then press a button to start the execution of your code:
document.querySelector('button').onclick = function () {
var block = [];
var temp;
var del;
var text = document.querySelector('textarea').value.replace(/\s+/g, '');
for(var a = 0;a < 9;a++){
for(var b = 0;b < 9;b++){
temp = parseInt(text[a*9+b]); // <-- get char from text area
if(temp>0){
block[a*10+b] = temp;
}else{
block[a*10+b] = [1,2,3,4,5,6,7,8,9];
}
}
}
for(var a = 0;a < 9;a++){
for(var b = 0;b < 9;b++){
var num = block[a*10+b]; // <-- get content, fix the index issue
if(typeof num == "number"){
for(var c = 0;c < 9;c++){
if(c != b && Array.isArray(block[a*10+c])){ //<-- add array-test
del = block[a*10+c].indexOf(num); // <-- not b, but num
if (del > -1) // <-- only splice when found
block[a*10+c].splice(del,1);
}
}
}
}
}
document.querySelector('pre').textContent = 'block='+ JSON.stringify(block);
};
<textarea rows=9>
53..7....
6..195...
.98....6.
8...6...3
4..8.3..1
7...2...6
.6....28.
...419..5
....8..79
</textarea>
<button>Process</button>
<pre></pre>
Note that there are elements in block which remain null. I suppose you intended this: as you multiply a with 10, and only store 9 values per "row", there is always one index that remains untouched.
I haven't looked over your second for loop, but you can try applying similar logic there as in the snippet I've provided. The issue is that you need to create a temporary array inside the outer for loop over values of a (but NOT inside the inner, nested for loop over values of b). Inside the for loop for values of b, then, you need to push something into that temporary array (which I called temp). Then, outside of the b for loop, but before the next iteration of a, push that temporary array temp to the block array. In this way, you will generate a 2D array.
var block = [];
var del;
for(var a = 0; a < 9; a++) {
let temp = [];
for(var b = 0; b < 9; b++) {
let num = parseInt(prompt(`Enter element ${b} of row ${a}:`));
if (num > 0) {
temp.push(num);
} else {
// block[a*10+b] = [1,2,3,4,5,6,7,8,9];
temp.push(b);
}
}
block.push(temp);
}
how do I count the frequency of the elements in the array, I'm new to Javascript and completely lost, I have looked at other answers here but can't get them to work for me. Any help is much appreciated.
function getText() {
var userText;
userText = document.InputForm.MyTextBox.value; //get text as string
alphaOnly(userText);
}
function alphaOnly(userText) {
var nuText = userText;
//result = nuText.split("");
var alphaCheck = /[a-zA-Z]/g; //using RegExp create variable to have only alphabetic characters
var alphaResult = nuText.match(alphaCheck); //get object with only alphabetic matches from original string
alphaResult.sort();
var result = freqLet(alphaResult);
document.write(countlist);
}
function freqLet(alphaResult) {
count = 0;
countlist = {
alphaResult: count
};
for (i = 0; i < alphaResult.length; i++) {
if (alphaResult[i] in alphaResult)
count[i] ++;
}
return countlist;
}
To count frequencies you should use an object which properties correspond to the letters occurring in your input string.
Also before incrementing the value of the property you should previously check whether this property exists or not.
function freqLet (alphaResult) {
var count = {};
countlist = {alphaResult:count};
for (i = 0; i < alphaResult.length; i++) {
var character = alphaResult.charAt(i);
if (count[character]) {
count[character]++;
} else {
count[character] = 1;
}
}
return countlist;
}
If you can use a third party library, underscore.js provides a function "countBy" that does pretty much exactly what you want.
_.countBy(userText, function(character) {
return character;
});
This should return an associative array of characters in the collection mapped to a count.
Then you could filter the keys of that object to the limited character set you need, again, using underscore or whatever method you like.
Do as below:
var __arr = [6,7,1,2,3,3,4,5,5,5]
function __freq(__arr){
var a = [], b = [], prev
__arr.sort((a,b)=>{return a- b} )
for(let i = 0; i<__arr.length; i++){
if(__arr[i] !== prev){
a.push(__arr[i])
b.push(1)
}else{
b[b.length - 1]++
}
prev = __arr[i]
}
return [a , b]
}