I am trying to calculate an angle in js using math js. I am experienced that when the division is between negative numbers js give me bad results. e.g. -6/-3 give me 20093 instead of 2.
How can I solve this? here below you can see a portion of console.log.
Here is the code:
var num = math.eval(parseInt(p[1]) - parseInt(d3.event.y));
var den = math.eval(parseInt(p[0]) - parseInt(d3.event.x));
if (den==0){
var angle = 0;
}else{
var m = math.eval(num/den);
if(m<1){
theta = m*100;
}else{
theta = m*100;
}
}
Syntax in code is num/den as you can see.
Thanks in advance
You can simply do -6/-3.
Run this in your developer tools console: alert(-6/-3); and you will see.
I think math.eval() expects a string like "-6/-3".
Related
Having some trouble getting this right. I'm very new to jQuery, so trying to get better and learn.
Currently I am getting 2 different values from a html table using the following code
var sellPrice = $('.qt').find("tr:eq(2)").find("td:eq(4)").html();
var buyPrice = $('.break .main-col .qt').find("tr:eq(2)").find("td:eq(4)").html();
These both output a value such as $13,000,000
I am then wanting to subtract 1 from these values (making it $12,999,999) before pasting them to an input as such
$('input[name="sell"]').val(sellPrice);
$('input[name="buy"]').val(buyPrice);
However, I am having some trouble with how to subtract $1 from these.
I tried using sellPrice--; but without success.
I've also tried adding - 1; at the end of each variable, but did not succeed either.
I tried to test something like this, but did not work either.
var minusOne = -1;
var getCurrentSellPrice = $('.qt').find("tr:eq(2)").find("td:eq(4)").html();
var getCurrentBuyPrice = $('.break .main-col .qt').find("tr:eq(2)").find("td:eq(4)").html();
var sellPrice = (getCurrentSellPrice - minusOne);
var buyPrice = (getCurrentBuyPrice - minusOne);
$('input[name="sell"]').val(sellPrice);
$('input[name="buy"]').val(buyPrice);`
Trying my best to familiarize myself with jQuery :)
Any help is much appreciated!
Solved using this
var getCurrentSellPrice = $('.qt').find("tr:eq(2)").find("td:eq(4)").html();
var getCurrentBuyPrice = $('.break .main-col .qt').find("tr:eq(2)").find("td:eq(4)").html();
var sellPrice = Number(getCurrentSellPrice.replace(/[^0-9\.]+/g,"")) - 1;
var buyPrice = Number(getCurrentBuyPrice.replace(/[^0-9\.]+/g,"")) + 1;
$('input[name="sell"]').val(sellPrice);
$('input[name="buy"]').val(buyPrice);
Since your numbers contain currency symbol and are strings, you need to convert them to proper numbers before subtracting them. See the answer below.
How to convert a currency string to a double with jQuery or Javascript?
Before reading below, do note that I have only recently started learning Javascript.
I am interested in making a text-based survival game. When trying to subtract a random number of survivors from the whole, I attempted to write what I think is, "A raid happens if the number is 0.50 - 1.00, and if the raid is successful, the group loses a random number of survivors between 1, and however many survivors there are." However, when I write this, I get an ESLint error, stating: ERROR: Parsing error: Unexpected Token if I don't know how I would rewrite it, or how to reformat it to work, if it is at all possible. The issue is in the code below, on lines 10, 11, & 12.
//constants
var EVENT_CHANCE = 0.15;
var EVENT_TYPE = 0.50;
var FOOD_CONSUMPTION = FOOD_CONSUMPTION;
var MATERIALS_CONSUMPTION = 1;
var ENEMY_STRENGTH = 10;
var SURVIVOR_STRENGTH = 1;
//equations
this.FOOD_CONSUMPTION = (this.food - this.surviors);
this.raid = if ( EVENT_TYPE > 0.50);{
this.survivors - Math.floor((Math.random() * this.surviors) + 1);
};
Let me know if I left anything important out
Note: I copied this post from the game development stack exchange, because they had advised me it is more of a stack overflow question, as it relates more to JS as a whole, than game development.
You have a semicolon after the condition
To conditionally assign a variable you need to use the ternary operator, for example:
const thing = condition ? ifTrue : ifFalse;
Or for your code:
this.raid = EVENT_TYPE > 0.50 ?
this.survivors - Math.floor((Math.random() * this.surviors) + 1) :
null;
//replace the null with what you want the variable to be if the condition is false
You can't use a statement as the right-hand side of an assignment, which is what you're trying to do here:
this.raid = if ( EVENT_TYPE > 0.50);{
this.survivors - Math.floor((Math.random() * this.surviors) + 1);
};
If you want to set this.raid to the result of EVENT_TYPE > 0.50, you just do that directly:
this.raid = EVENT_TYPE > 0.50;
If you then want to use that in a branch, you can follow it with the if testing this.raid:
this.raid = EVENT_TYPE > 0.50;
if (this.raid) {
this.survivors - Math.floor((Math.random() * this.survivors) + 1);
}
(I also fixed a typo in that, the second survivors was missing a v. But there's still a problem I didn't know how to fix: It calculates a value without storing it anywhere. It's not an error in JavaScript, but it probably isn't what you wanted. You may have meant -= instead of -.)
Note that neither of the ; that were originally in that if belonged there. You don't put ; after the () in an if, and you don't put a ; after the block attached to a flow-control statement (if, while, etc.).
I am developing a simple application form where I am calculating experiences from maximum three employers. Now I want to add them up . The experiences are in the form of X years Y months and Z days. I have written following javascript function --
function total(){
var td;
var fd=parseInt(document.getElementById("LoS_days1").value);
var sd=parseInt(document.getElementById("LoS_days2").value);
var ld=parseInt(document.getElementById("LoS_days3").value);
var tm;
var fm=parseInt(document.getElementById("LoS_months1").value);
var sm=parseInt(document.getElementById("LoS_months2").value);
var lm=parseInt(document.getElementById("LoS_months3").value);
var ty;
var fy=parseInt(document.getElementById("LoS_year1").value);
var sy=parseInt(document.getElementById("LoS_year2").value);
var ly=parseInt(document.getElementById("LoS_year3").value);
td = (fd +sd +ld);
var rd = td%30;
var cm = Math.floor(td/30);
document.getElementById("Totalexp_day").value=rd;
tm = (cm + fm +sm +lm);
var rm = tm%12;
var cy = Math.floor(ty/12);
document.getElementById("Totalexp_month").value=rm;
ty = (cy + fy +sy +ly);
document.getElementById("Totalexp_year").value=ty;
}
I am getting a NaN message in each of the Totalexp_day, Totalexp_month and Totalexp_day field. Earlier I had some modified code that was not showing NaN message but it was not showing the desired results. Kindly suggest what to do to eliminate these two errors.
parseInt(document.getElementById("LoS_days1").value)
if the first character of the string cannot be converted to a number, parseInt will return NaN.
To avoid this, you can so something like is suggested here:
parseInt(document.getElementById("LoS_days1").value) || 0
If document.getElementById("Totalexp_day").value is empty then also it will return NaN. Make sure you have some number there.
Second alternative is reading document.getElementById("Totalexp_day").innerHTML and then applying parseInt
Probably you alert or console log the document.getElementById("Totalexp_day").value you would be more clearer why this problem is comming
Allright, I know what machine precision is, but this, I can't understand...
Code:
console.log("meanX",meanX);
meanX2 = meanX * meanX; //squared
console.log("meanX2",meanX2);
Console output:
meanX 300.3
meanX2 28493.4400000000002
In case you are wondering, the correct value for meanX2 would be 90180.09
And this is only one of the many examples visible in the screenshot..
.toFixed(6) seems to fix this... But I have no idea why it doesn't work without it.
Edit
Ok, I don't want to post the whole program code here because in first place I'm not the only author, and second, I also wouldn't like this to be copied without our permission. But I'll gladly explain how I get this error and will post the whole method/function code here.
This code belongs, as you may have guessed from the window title, to a lane detection algorithm. We use Three.js/webgl to run some pre processing shaders on each frame of a video and then we analyze the resulting image. The method/function you see on the screenshot is a perpendicular line fitting algorithm and is part of the whole thing.
I can see the algorithm running nicely because I have the lane being drawn on top of the video, and It is well placed. Until suddenly the lane turns into an horizontal bar. This unexpected behavior happens exactly because of the phenomenon I described here, since it's from that moment that I start to see wrong math in the console.
Also, because the video and algorithm run at slightly different fps everytime, the problem doesn't always happen in the same moment of the video, and sometimes It doesn't happen at all.
Here is the code (it has some alterations because I was trying to isolate the issue):
this.perpendicularLineFit = function (points, slopeSign) {
var count = points.length;
var sumX = 0,
sumY = 0;
var sumX2 = 0,
sumY2 = 0,
sumXY = 0;
var meanX, meanY;
var i, lowp = {}, highp = {};
var B;
var slope;
var originY;
for (i = 0; i < count; i++) {
sumX += points[i].x;
sumY += points[i].y;
sumX2 += points[i].x * points[i].x;
sumY2 += points[i].y * points[i].y;
sumXY += points[i].y * points[i].x;
}
meanX = sumX / count;
meanY = sumY / count;
//If you uncoment this, problem reappears:
//var numeratorLeft = meanY * meanY;
console.log("meanX",meanX);
var meanX2 = meanX*meanX;
console.log("meanX2",meanX2);
var numerator = (sumY2 - count * (meanY * meanY)) - (sumX2 - count * meanX2);
var denominator = (count * meanX * meanY - sumXY);
B = 0.5 * (numerator / denominator);
slope = -B + slopeSign * Math.sqrt(B * B + 1);
originY = meanY - slope * meanX;
slope = isNaN(slope) ? slopeSign : slope;
originY = isNaN(originY) ? originY : originY;
lowp.y = this.lowY;
lowp.x = (this.lowY - originY) / slope;
highp.y = this.highY;
highp.x = (this.highY - originY) / slope;
return {
low: lowp,
high: highp
};
};
Now, I was trying to understand what was causing this, and the most bizarre thing is that it seems that when I place a statement of this form
var x = ... meanY * meanY ...;
before the meanX2 attribution, the issue happens. Otherwise it doesn't.
Also, I tried to catch this anomaly in the debugger but just when I enter the debugging tab, the problem disapears. And the values turn correct again.
I certainly don't believe in black magic, and I know that you are probably skeptic to this.
I would be too. But here is a link to a video showing it happening:
The video
Edit2:
I managed to reproduce this issue in another computer.. Both having ubuntu and using firefox (versions 20 and 21).
Edit3:
I'm sorry it took so much time! Here is a zip containing the issue. Just run it in any webserver. The code mentioned is in LaneDetection.js. Search for "HERE" in the file to find it.
https://docs.google.com/file/d/0B7y9wWiGlcYnYlo1S2pBelR1cHM/edit?usp=sharing
The problem might not happen in the first attempts. If that's the case refresh the page and try again. When the lines get horizontal you know it's there. As I said, I saw this problem happening in firefox versions 20 and 21 on ubuntu. In chrome it never happened.
By the way, I noticed that changing javascript.options.typeinference flag in firefox seems to stop the problem... I don't know exactly what that flag does, but maybe this optimization is not correctly implemented in firefox?
I can't say for sure that I actually have an answer but I think that I have confirmed that basilikum was correct to suggest a memory problem. Here's what I did: I took the first ten entries from your screenshot and calculated the correct answer. I then converted the correct answer and the wrong answer into the hexidecimal representation of the double-precision float. What I ended up with was the following:
292.416^2 = 85507.506 = 40F4E0381C71C71E
changed to 27583.373 = 40DAEFEB1C71C722
293.166^2 = 85946.694 = 40F4FBAB1C71C72A
changed to 27583.373 = 40DAEFEB1C71C722
295.818^2 = 87508.396 = 40F55D4658DC0876
changed to 28041.024 = 40DB62419637021F
294.500^2 = 86730.250 = 40F52CA400000000
changed to 27583.373 = 40DAEFEB1C71C722
297.000^2 = 88290.000 = 40F58E2000000000
changed to 28041.024 = 40DB62419637021F
221.750^2 = 49173.062 = 40E802A200000000
changed to 24964.000 = 40D8610000000000
300.300^2 = 90180.090 = 40F6044170A3D70A
changed to 28493.440 = 40DBD35C28F5C290
220.200^2 = 48488.040 = 40E7AD0147AE147B
changed to 25408.360 = 40D8D0170A3D70A4
300.600^2 = 90360.360 = 40F60F85C28F5C29
changed to 28493.440 = 40DBD35C28F5C290
213.000^2 = 45369.000 = 40E6272000000000
changed to 28032.326 = 40DB6014E5E0A72E
There's no persistent pattern to the change but there are a couple instances that are very telling of a memory issue. In the first two entries you can see that bytes 1, 2 and 3 were unchanged. In the 9th entry there's something even more odd. It would appear that bytes 0 - 3 were shifted left by exactly 4 bits! Upon considering the statement that the problem doesn't arise until after some time has passed and in light of these two anomalies, I'm fairly confident that you're encountering some sort of memory issue. Could it be, dare I say, a stack overflow?
I'm trying to get the percentage between two numbers for the purpose of showing the difference as far as a discount. I've tried to simplify it as much as I can but I still cant get what I want.
Here is an example.
var RegPrice = 8.95;
var OnSale = 6.67;
var OnSaleAT = Math.abs(Math.max(100.00 - OnSale / RegPrice * 100.00));
alert(OnSaleAT.toFixed(2));
What I'm trying to get is the alert(); to return a value of 25.50. However, I'm getting 25.47.
Any ideas on how I can get this right?
25.47486... is the correct answer. If you're attempting to round to the nearest tenths, you can use:
var result = Math.round(OnSaleAT * 10) / 10;
Which outputs: 25.5 and from there you can format your answer how you like.
$(window).load(function() {
var RegPrice = 8.95;
var OnSale = 6.67;
var OnSaleAT = Math.round(Math.abs(Math.max(100.00 - 6.67 / 8.95 * 100.00)) * 10.00) / 10.00
alert(OnSaleAT.toFixed(2));
});
If you're trying to round to 25.5%, you can just alert with a toFixed param of 1 instead of 2:
alert(OnSaleAT.toFixed(1));
Other than that, Rob W is right...the math does come out to 25.47, and there's not much you can do about that.
try OnSaleAT.toFixed(1)+'0' :)
Math.ceil(1000* (1 - OnSale/RegPrice))/10
give you "25.5"
:)