How do you convert mixed fractions to decimal?

Question

How do I convert "1 1/4" to 1.25?

I want to take user input and convert it to the logical numerical equivalent. I say logical because 2 R and R 2 need to be 2(has to do with measuring chiropractic adjustments). Everything worked until they needed to be able to use mixed fractions.

Is there a library for this?

The only number that does not work is "1 1/4" which is converted in error to "2.75".

    // Sample input
    var values = ["2.5", "1 1/4", "1/4", "2 R", "R 2"];

    function l(msg) {
        console.log(msg)
    }

    function toDecimal(x) {
        if (x.indexOf('/') != -1) {
            var parts = x.split(" ")
            var decParts = parts[1].split("/")
            return parseInt(parts[0], 10) + (parseInt(decParts[0], 10) / parseInt(decParts[1], 10))
        } else {
            return x
        }
    }

    function total_it_up(values){
        var total = 0,
            value = 0

        if(values === undefined)
            return 0

        $.each(values, function(index, value){
            value = value.replace(/[^0-9./]+/g, "")
            value = eval(value)
            l(value)
            total += parseFloat(value)
        })

        return total
    }

SOLUTION

    function toDecimal(x) {
        if (x.indexOf('/') != -1) {
            var parts = x.split(" ")
            var decParts;
            if (parts.length > 1) {
                decParts = parts[1].split("/");
            }
            else {
                decParts = parts[0].split("/");
                parts[0] = 0;
            }
            return parseInt(parts[0], 10) + (parseInt(decParts[0], 10) / parseInt(decParts[1], 10))
        } else {
            return x
        }
    }


    function total_it_up(values){
        var total = 0;

        if(values === undefined)
            return 0;

        $.each(values, function(index, value){
            total += parseFloat(toDecimal($.trim(value.replace(/[^0-9./ ]+/g, ""))));
        })

        return total;
    }

I'm not sure if there's a library for this already, but it should be fairly straightforward maths once you've split out the values. — Rory McCrossan, Nov 02 '12 at 17:36
@rory I'm working on a simple function I'll post unless someone beats me to it. — Michael J. Calkins, Nov 02 '12 at 17:38
I don't see where you ever call your toDecimal function, which, aside from a few safety checks, looks like it ought to work. Also why `eval`? eval is evil. — Matt Burland, Nov 02 '12 at 17:42
possible duplicate of [Convert Fraction String to Decimal?](http://stackoverflow.com/questions/7142657/convert-fraction-string-to-decimal) — SpYk3HH, Nov 02 '12 at 17:46
@MattBurland `eval` is evil IFF you're using it to evaluate user input. Otherwise, it's merely a bad idea. — Blazemonger, Nov 02 '12 at 17:48
Also: please use semicolons to terminate each line of code. It'll cause you problems someday if you don't. — Blazemonger, Nov 02 '12 at 17:49
@Blazemonger: true, but since the question states: "I want to take user input and convert it to the logical numerical equivalent." I stand by my comment. — Matt Burland, Nov 02 '12 at 17:51
@blazemonger semi colons are optional in Javascript. http://mislav.uniqpath.com/2010/05/semicolons/ I'm converting their input to numbers so eval isn't a problem for injection. Unless you have a specific example. — Michael J. Calkins, Nov 02 '12 at 17:57
Since you asked: http://stackoverflow.com/q/5397275/901048 -- but if nothing else, it makes your code more readable to other humans. — Blazemonger, Nov 02 '12 at 18:07
@blazemonger That's all I needed to see :) What I'm doing now: http://jsfiddle.net/hcgGV/ I just get a split error but it parses everything correctly. — Michael J. Calkins, Nov 02 '12 at 18:18
@SpYk3HH That other question isn't a duplicate, because it only handles a single fraction, not mixed fractions. — Barmar, Nov 03 '12 at 04:17

score 2 · Accepted Answer · answered Nov 02 '12 at 17:46

2

We don't see any call for toDecimal(), so I'm assuming the $.each loop is calling it in your original code. If that is the case, then 1 1/4 is coming up as 2.75 because the regular expression is stripping the space between 1 and 1/4, resulting in 11/4, which is 2.75. Allow spaces, but $.trim the result so that any leading or trailing spaces are removed. You also shouldn't have to use eval().

answered Nov 02 '12 at 17:46

Mathachew

2,044
2
18
31

I'm going to go at this with each of the inputs one at a time I'll update my question with the answer when I get it. – Michael J. Calkins Nov 02 '12 at 17:59
Can you show us where exactly you're using `toDecimal()`? The only place I can see 2.75 occurring is when `value.replace(/[^0-9./]+/g, "")` is applied to the typed value, which turns `1 1/4` into `11/4`. Using `$.trim(value.replace(/[^0-9./ ]+/g, ""))` leaves `1 1/4` as is and will return the expected `1.25`. – Mathachew Nov 02 '12 at 18:04
Here's an example, with `toDecimal()` updated to properly handle `1/4`. Handling the various inputs could probably be better written, but it's a working example: http://jsfiddle.net/MVtnU/ – Mathachew Nov 02 '12 at 18:14
I think you pasted the wrong jsFiddle link. It has the same code I posted, and my update addresses the split error you're hitting (a space doesn't exist in `1/4`). – Mathachew Nov 02 '12 at 18:22
Have you looked at the jsFiddle link I posted? It fixes the error you're seeing. Your fiddle updated with the fix: http://jsfiddle.net/hcgGV/2/ – Mathachew Nov 02 '12 at 18:26

srijan · Answer 2 · 2012-11-02T17:53:35.190

0

I accidently posted perl instead of JS before. Here is the correct one. Please do the cleaning.

Example

    <html>
  <body>
    <script language=javascript>


 var txt='4 1/2';

      var re1='(\\d+)'; // Integer Number 1
      var re2='.*?';    // Non-greedy match on filler
      var re3='(\\d+)'; // Integer Number 2
      var re4='.*?';    // Non-greedy match on filler
      var re5='(\\d+)'; // Integer Number 3

      var p = new RegExp(re1+re2+re3+re4+re5,["i"]);
      var m = p.exec(txt);
      if (m != null)
      {
          var int1=m[1];
          var int2=m[2];
          var int3=m[3];
          document.write("("+int1.replace(/</,"&lt;")+")"+"("+int2.replace(/</,"&lt;")+")"+"("+int3.replace(/</,"&lt;")+")"+"\n");
      }
    </script>
  </body>
</html>

edited Nov 02 '12 at 17:53

answered Nov 02 '12 at 17:39

srijan

1,504
1
13
24

Just curious, why did you put `$` in front of the variables? – Paul Richter Nov 02 '12 at 17:39
Because I use this http://txt2re.com/index.php3?s=1%201/4&2&3&4 to generate that. And may be I'm more comfortable with jQuery. – srijan Nov 02 '12 at 17:42
Oh its perl. Gotcha. Interesting site too. – Paul Richter Nov 02 '12 at 17:45
@srijan: Wow! That's a handy little link there. – Matt Burland Nov 02 '12 at 17:49

score 0 · Answer 3 · answered Nov 02 '12 at 17:45

0

This is terrible.

function ConvertFraction(fraction)
{
     eval(fraction.replace('R','').trim().replace(' ', '+'))
}

answered Nov 02 '12 at 17:45

Porco

4,163
3
22
25

How do you convert mixed fractions to decimal?

SOLUTION

3 Answers3