Subtract values in table with similar class name

Question

I have a table in which I want to subtract values in columns. However, instead of subtracting the values it keeps adding up.

jsFiddle.

HTML:

<table>
    <tr class="parent-ca">
        <td>
             <h4><em>Contract Amount</em></h4>

        </td>
        <td>
            <input type="text" class="rr" /> //all rr should be subtracted
        </td>
        <td>
            <input type="text" class="rr1" /> //all rr1 should be subtracted
        </td>
        <td>
            <input type="text" class="rr2" />
        </td>
        <td>
            <input type="text" class="rr3" />
        </td>
    </tr>
    <tr class="parent-abc">
        <td>
             <h5><em>Contract Amount</em></h5>

        </td>
        <td>
            <input type="text" class="rr" />
        </td>
        <td>
            <input type="text" class="rr1" />
        </td>
        <td>
            <input type="text" class="rr2" />
        </td>
        <td>
            <input type="text" class="rr3" />
        </td>
    </tr>
    <tr class="parent-a">
        <td>
             <h5><em>Contract Amount</em></h5>

        </td>
        <td>
            <input type="text" class="rr" />
        </td>
        <td>
            <input type="text" class="rr1" />
        </td>
        <td>
            <input type="text" class="rr2" />
        </td>
        <td>
            <input type="text" class="rr3" />
        </td>
    </tr>
    <tr class="parent-b">
        <td>
             <h5><em>Contract Amount</em></h5>

        </td>
        <td>
            <input type="text" class="rr" />
        </td>
        <td>
            <input type="text" class="rr1" />
        </td>
        <td>
            <input type="text" class="rr2" />
        </td>
        <td>
            <input type="text" class="rr3" />
        </td>
    </tr>
    <tr class="parent-c">
        <td>
             <h5><em>Contract Amount</em></h5>

        </td>
        <td>
            <input type="text" class="rr" />
        </td>
        <td>
            <input type="text" class="rr1" />
        </td>
        <td>
            <input type="text" class="rr2" />
        </td>
        <td>
            <input type="text" class="rr3" />
        </td>
    </tr>
    <tr class="nettotal tt table-sub" data-minus="ca,contract,other2">
        <td>
             <h4>Net Cash</h4>

        </td>
        <td>
            <input type="text" id="rr" />
        </td>
        <td>
            <input type="text" id="rr1" />
        </td>
        <td>
            <input type="text" id="rr2" />
        </td>
        <td>
            <input type="text" id="rr3" />
        </td>
    </tr>
</table>

jQuery:

function calcSubMTotal(p) {
    var minus = 0;
    var minus_total = $('#' + p + '');


    $('.' + p + '').each(function (i) {
        if (!isNaN(this.value) && this.value.length !== 0) {
            minus -= this.value; //trying to subtract but this just adds up rather than subtract
        }
    });

    minus_total.val(minus);


}

$('input[type=text]').on('keyup', function () {
    calcSubMTotal("rr");
    calcSubMTotal("rr1");
    calcSubMTotal("rr2");
    calcSubMTotal("rr3");
});

Answer 1

Updated FIDDLE

Jquery

        function calcSubMTotal(p) {
    var minus = 0;
    var isFirst=true;
    var minus_total = $('#' + p + '');


    $('.' + p + '').each(function (i) {
        if (!isNaN(this.value) && this.value.length !== 0) {
            if(!isFirst)
            minus -= parseInt(this.value); 
            else
            {
                minus=parseInt(this.value);
                isFirst=false;
            }
        }
    });

    minus_total.val(minus);


}

$('input[type=text]').on('keyup', function () {
    calcSubMTotal("rr");
    calcSubMTotal("rr1");
    calcSubMTotal("rr2");
    calcSubMTotal("rr3");
});