I have searched and although I see this addressed in Python and PHP, I don't see it using JS. This script randomizes order on refresh and I would like the numbers to be randomly generated as well as the order. The order part is already working, but I don't want it limited to numbers I input (150, 375 and 900 in this example). I'm going to have about 50 variables but I've just listed three to keep it short here.
I would also like to understand how to control the place values permitted, so I could have xx,xx,xx, etc./ xxx,xxx,xxx etc. and also how to state a range, so it could include xx,xxx,xxxx
Lastly I would be very keen to understand how to limit the generated numbers to meet certain profiles, like all tens (670,320,980,410,650), twenty-fives (375,925,400,850,175, etc.). This would be extremely helpful.
I'm sorry this is just beyond my ability, and I have tried and tried. I operate a school in India where I teach math, and we have had great success teaching number recognition and counting in English and Hindi using printed charts of numbers that fit different criteria like this, and I would like to adapt it to a mobile app, just to let you know why I'm asking. Many thanks.
var contents=new Array()
contents[0]='150'
contents[1]='375'
contents[2]='900'
*/
var spacing = "<br />"
var the_one
var z = 0
while (z<contents.length){
the_one=Math.floor(Math.random()*contents.length)
if (contents[the_one]!="_selected!"){
document.write(contents[the_one]+spacing)
contents[the_one]="_selected!"
z++
}
}
Related
I have a lot of points represented by an id and their position as lat long coordinates. Every 10 seconds, a point is able to move and its position is updated. There may be 100,000 points at most but this number can also vary through time.
I need to send all this data to a user when it connects to my server.
To achieve this, I put them in a typed array like so :
var data = new Float32Array(points.length * 3);
for (var i = 0; i < points.length;i++) {
data[i*3]=points[i].id;
data[i*3+1]=points[i].position.lat;
data[i*3+2]=points[i].position.long;
}
The thing is, doing this takes about 0.9 millisecond on my computer which isn't so bad but not quite satisfying. The surprising thing is that of course when lines 3,4 and 5 are commented out, the algorithm is a lot faster, but once one is not commented, it doesn't change a lot whether the two others are or not, the time will be very similar.
I would like to know if I am doing something wrong here or if there is a faster way to achieve what I want.
Thanks in advance,
I'm generating random IDs in javascript which serve as unique message identifiers for an analytics suite.
When checking the data (more than 10MM records), there are some minor collisions for some IDs for various reasons (network retries, robots faking data etc), but there is one in particular which has an intriguing number of collisions: akizow-dsrmr3-wicjw1-3jseuy.
The collision rate for the above id is at around 0.0037% while the rate for the other id collisions is under 0.00035% (10 times less) out of a sample of 111MM records from the same day. While the other ids are varying from day to day, this one remains the same, so for a longer period the difference is likely larger than 10x.
This is how the distribution of the top ID collisions looks like
This is the algorithm used to generate the random IDs:
function generateUUID() {
return [
generateUUID4(), generateUUID4(), generateUUID4(), generateUUID4()
].join("-");
}
function generateUUID4() {
return Math.abs(Math.random() * 0xFFFFFFFF | 0).toString(36);
}
I reversed the algorithm and it seems like for akizow-dsrmr3-wicjw1-3jseuy the browser's Math.random() is returning the following four numbers in this order: 0.1488114111471948, 0.19426893796638328, 0.45768366415465334, 0.0499740378116197, but I don't see anything special about them. Also, from the other data I collected it seems to appear especially after a redirect/preload (e.g. google results, ad clicks etc).
So I have 3 hypotheses:
There's a statistical problem with the algorithm that causes this specific collision
Redirects/preloads are somehow messing with the seed of the pseudo-random generator
A robot is smart enough that it fakes all the other data but for some reason is keeping the random id the same. The data comes from different user agents, IPs, countries etc.
Any idea what could cause this collision?
I am trying to generate a random level for my silly game. The game consists of having laser/detector pairs around a square field of possible mirrors. Like this:
/*
LLLLLLLLLL
LmmmmmmmmL
LmmmmmmmmL
LmmmmmmmmL
LLLLLLLLLL
*/
Now, I have an algorithm which generates a level, quite poorly, by relying on random placement, and rejecting bad positions. This is not very fast, and does not really generate the kind of fields I'd like to have. Please feel free to try it out at http://cmouse.desteem.org/laser/
Any suggestions are welcome.
The current algorithm looks something like this:
function createLevel:
for i=0 to mirrors:
mirrorLocation = pickRandomPosition
mirrorType = pickRandomType
if (verifyPosition(mirrorLocation, mirrorType)):
i = i - 1
next
else:
storeMirror(mirrorLocation, mirrorType)
In verifyPosition, we test the mirror that it reaches a laser in all four directions, in hope of avoiding undetectedable mirrors. It is somewhat boring code, so I omit it here.
One way to make sure it's not trying multiple fields more than once is to iterate over the fields and put a mirror or not based on some probability. The probability to put a mirror should be #mirros / #fields, so that the expected number of mirrors is #mirrors at the end.
I have an multi dimensional array as
[
{"EventDate":"20110421221932","LONGITUDE":"-75.61481666666670","LATITUDE":"38.35916666666670","BothConnectionsDown":false},
{"EventDate":"20110421222228","LONGITUDE":"-75.61456666666670","LATITUDE":"38.35946666666670","BothConnectionsDown":false}
]
Is there any plugin available to search for combination of LONGITUDE,LATITUDE?
Thanks in advance
for (var i in VehCommLost) {
var item = VehCommLost[i];
if (item.LONGITUDE == 1 && item.LATITUDE == 2) {
//gotcha
break;
}
}
this is json string..which programming language u r using with js??
by the way try with parseJSON
Are the latitudes and longitudes completely random? or are they points along a path, so there is some notion of sequence?
If there is some ordering of the points in the array, perhaps a search algorithm could be faster.
For example:
if the inner array is up to 10,000 elements, test item 5000
if that value is too high, focus on 1-4999;
if too low, focus on 5001-10000, else 5000 is the right anwser
repeat until the range shrinks to the vicinity, making a straight loop through the remaining values quick enough.
After sleeping on it, it seems to me most likely that the solution to your problem lies in recasting the problem.
Since it is a requirement of the system that you are able to find a point quickly, I'd suggest that a large array is the wrong data structure to support that requirement. It maybe necessary to have an array, but perhaps there could also be another mechanism to make the search rapid.
As I understand it you are trying to locate points near a known lat-long.
What if, in addition to the array, you had a hash keyed on lat-long, with the value being an array of indexes into the huge array?
Latitude and Longitude can be expressed at different degrees of precision, such as 141.438754 or 141.4
The precision relates to the size of the grid square.
With some knowledge of the business domain, it should be possible to select a reasonably-sized grid such that several points fit inside but not too many to search.
So the hash is keyed on lat-long coords such as '141.4#23.2' with the value being a smaller array of indexes [3456,3478,4579,6344] using the indexes we can easily access the items in the large array.
Suppose we need to find 141.438754#23.2i7643 : we can reduce the precision to '141.4#23.2' and see if there is an array for that grid square.
If not, widen the search to the (3*3-1=) 8 adjacent grids (plus or minus one unit).
If not, widen to the (=5*5-9) 16 grid squares one unit away. And so on...
Depending on how the original data is stored and processed, it may be possible to generate the hash server-side, which would be preferable. If you needed to generate the hash client-side, it might be worth doing if you reused it for many searches, but would be kind of pointless if you used the data only once.
Could you comment on the possibility of recasting the problem in a different way, perhaps along these lines?
I'm using this bit of code to display the number of users on a site.
My customer is complaining it looks fake. Any suggestions?
var visitors = 187584;
var updateVisitors = function()
{
visitors++;
var vs = visitors.toString(),
i = Math.floor(vs.length / 3),
l = vs.length % 3;
while (i-->0) if (!(l==0&&i==0))
vs = vs.slice(0,i*3+l)
+ ','
+ vs.slice(i*3+l);
$('#count').text(vs);
setTimeout(updateVisitors, Math.random()*2000);
};
setTimeout(updateVisitors, Math.random()*2000);
Edited:
alt text http://img695.imageshack.us/img695/4268/reachdevs2.png
Screenshot-Advertise - Stack Overflow - Chromium http://img130.imageshack.us/img130/8083/screenshotadvertisestac.png
http://inedomedia.com/stackoverflow.aspx
Everyone knows JS counters are fake, don't bother trying to make it look "less fake", bother making a real one.
If you don't have enough visitors to show around, just don't use a counter, they're so 90's.
Warning: Attempted Humour
Did he ask for a giant splash page to go along with the fake real-time visitor counter? How about some nice "Netscape Now!" button logos and blinking text? Here are some really cool "under construction" animated gifs you can use too.
http://www.animatedgif.net/underconstruction/construction.shtml
-Oisin
I'm guessing it looks fake because every time you load the page it starts at the same number and counts upwards?
Take a look at the javascript that tells you how many megabytes of email storage you get with a Gmail account. I think it bases the starting number on the date/time, so that if you load a page, watch it count up, and then load it again, it won't reload with a smaller number.
Be honest though... it is fake right? You aren't showing precisely how many users there are and updating it live as new users create accounts. The goal then is to make sure it is somewhat close to reality. Hopefully the rate at which the number increases in your script is based on past new-user subscription rates.
make the interval parameter of the setInterval random as well ... it will look more real as it will randomly increment the random numbers :)