this.options={ notation: 'auto', precision : 8,  exponential: { lower: 1e-10,  upper: 1e+10 }};

this.satvp = function(x)
{
    // saturation vapor pressure (temperature), kPa
    return 0.611 * math.exp(17.502*x/(parseInt(x) + 240.97)) ;
}

this.dewp = function(x)
{
    // dewpoint (vapor pressure), C
    return 240.97 * math.log(x/0.611) / (17.502 - math.log(x/0.611));
}

this.vptovd = function(x,y)
{
    // convert vapor pressure to vapor density, kPa to g/m3
    return 2166 * x / (273.16 + y)
}

this.vptomr = function(x)
{
    // Mixing ratio (vapor pressure), kg/kg
    return (0.622 * x / 101.3) /(1 - x / 101.3)
}