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I'm trying to calculate the average net price of a product. I have, in my Product model :total_sold and :total_net_revenue. Doing straight division in the method seems to always result in 0. I resorted to using BigDecimal as I figured that was the problem ... but with my latest iteration of the code below, I'm still getting zero when the answer comes out to a decimal.
def avg_price
BigDecimal(total_sold.to_s) / (BigDecimal(total_net_revenue.to_s) / 100)
end
Net revenue is in cents, which is why I divide by 100. Can someone point out what I'm doing wrong or should do?
883
Ruby has a built in function round() which allows us to both change floats to integers, and round floats to decimal places. round() with no argument will round to 0 decimals, which will return an integer type number. Using round(1) will round to one decimal, and round(2) will round to two decimals.
For clarity's sake: the precision is the number of significant digits, while the scale is the number of digits that can be stored following the decimal point. For example, the number 123.45 has a precision of 5 and a scale of 2. A decimal with a precision of 5 and a scale of 2 can range from -999.99 to 999.99.
You can simply use x. round(2) when displaying the number - that will always display two decimal places. It's generally recommended to store prices as integers in the backend database because they are handled better when you need a really high level of precision. In this case though, you can choose to go either way.
total_net_revenue / total_sold
or
total_net_revenue / total_sold / 100.0
or
total_net_revenue.to_f / total_sold / 100
These three methods give an increasing amount of precision, if you want it. Remember that "average price" is "average price / sale. That's money-per-item so you will want to do the division in that specific order.
89
First: You are dividing the wrong way.
100 items / $150 = .667 items per dollar
vs.
$150 / 100 items = $1.50 per item
Second: Like other languages, you need to force one of the numbers in the equation to be a decimal so that the result is cast as one as well. Since your revenue is a whole number, that meant all three values were whole numbers, which means you got a whole number as a result. To get a decimal, cast one of them as a floating-point number.
In other words, to get what you need, do this:
price_per_item = (total_net_revenue.to_f / 100) / total_sold
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