
Re: Square Root and Wind Chill
Sunny Talwar Feb 10, 2017 3:13 AM (in response to Joe Easley)May be like this
LOAD Temp,
Wind,
35.74 + (0.6215 * Temp)  pow(35.75 * Wind, 0.16) + pow(0.4275 * Temp * Wind, 0.16) as [Wind Chill]


Re: Square Root and Wind Chill
Sunny Talwar Feb 10, 2017 7:17 PM (in response to Joe Easley)I think there was a slight misunderstanding of the expression. I checked online and this seems to work:
Table:
LOAD *,
35.74 + (0.6215 * Temp)  (35.75 * pow(Wind, 0.16)) + (0.4275 * Temp * pow(Wind, 0.16)) as [Wind Chill];
LOAD * INLINE [
Temp, Wind
37, 5
37, 8
43, 11
46, 4
46, 6
52, 2
];

249394.qvw 150.2 K

Re: Square Root and Wind Chill
Joe Easley Feb 10, 2017 8:56 PM (in response to Sunny Talwar )so that worked perfectly. and then i ran into another problem. it turns out there is a point at which the wind chill is replaced with the heat index. the logic is if the temp is greater than 80 and relative humidity is greater than 40%, then use heat index for apparent temp, else use windchill for apparent temp.
so what i would like to do is figure out how to have individual windchill (solved) and heat index variables, as well as an apparent temp variable that factors the logic.
heat index formula below (wikipedia entry). you have been SO helpful, and i appreciate anything else youre willing to help with.
i have temp in the model as well as humidity (CmpHumidity)

Re: Square Root and Wind Chill
Sunny Talwar Feb 11, 2017 7:49 PM (in response to Joe Easley)The expression in QlikView should be like this:
42.379 +
(2.04901523 * Temp) +
(10.14333127 * CmpHumidity) +
(0.22475541 * Temp * CmpHumidity) +
(683783 * pow(10,3) * pow(Temp, 2)) +
(5.481717 * pow(10, 2) * pow(CmpHumidity, 2)) +
(1.22874 * pow(10, 3) * pow(Temp, 2) * CmpHumidity) +
(8.5282 * pow(10, 4) * Temp * pow(CmpHumidity, 2)) +
(1.99 * pow(10, 6) * pow(Temp, 2) * pow(CmpHumidity, 2))
Not sure how this is related to Wind Chill... Can you elaborate on that part?

Re: Square Root and Wind Chill
Joe Easley Feb 11, 2017 9:05 PM (in response to Sunny Talwar )when measuring "apparent temperature" for analysis, sometimes you need windchill, sometimes you need heat index. i learned this as i was getting deeper into the app.

Re: Square Root and Wind Chill
Sunny Talwar Feb 11, 2017 9:07 PM (in response to Joe Easley)So this information will reside in one field with flags or are you looking to create two fields? One for windchill and one for heat index?

Re: Square Root and Wind Chill
Joe Easley Feb 11, 2017 9:53 PM (in response to Sunny Talwar )i just made an adhoc =variable to handle it:
if
(CmpTemp >= 70,($(vHeatindex)),
if(CmpTemp <= 60,($(vWindchill)),CmpTemp))
i can now grap HeatIndex OR WIndchill independently OR run one field as apparent temp.
you have been such a tremendous help!!






