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I am having a problem writing an income function. The information I have been given is: " Charles has taken over a market stall where he sells fresh fish. Each morning he buys fish from the wholesaler at a cost of £4 per kg up to the first 100 kg and £2.5 per kg for anything above 100 kg. He sells the fish at £8 per kg. If any fish remains unsold at the end of the day, he sells it to the cat food factory for £1 per kg. Charles would like to know how much fish to buy each day in order to maximise his average daily profit."

So far I modelled given data for the daily sales figures for the last 150 as a gamma function and used the Method of moments to find the parameters, below is the code I used:

First_moment_Xbar = sum(nfsold)/150
Second_moment = sum((nfsold)^2)/150\
estimator_of_lambda = (First_moment_Xbar)/(Second_moment - (First_moment_Xbar)^2)
estimator_of_k = (First_moment_Xbar)^2 / (Second_moment - (First_moment_Xbar)^2 )

estimator_of_k
estimator_of_lambda

and I got:

> estimator_of_k
[1] 4.992957
> estimator_of_lambda
[1] 0.05733275

I wrote a cost function of buying n kg of fish as:

cost=function(n)

{
  total = 0
  if(n<=100)
    {
    total = n*4
  }
  else{
    total =  100*4 + (n-100)*2.5
  }

  return(total)

}

Now, I have to write an income function, income(n,d) when there are potential sales of d kg and Charles has bought n kg of fish.

I think potential sales will be modelled around:

round(rgamma(1, estimator_of_k, estimator_of_lambda), digits = 0)

as I know the sales for fish prior to cat food will be modelled around the Gamma I found.

Please may I have some help as to how to find the income function, thank you.

Kurtis Rader
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Han
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  • Can you give us a minimum sample of your data by pasting the output of `dput(df)` where `df` is your data set? – hpesoj626 Apr 29 '18 at 16:55
  • I'm sorry I'm still a little confused, what does this mean?? – Han Apr 29 '18 at 17:25
  • Read through this [post](https://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example). Answerers will find it hard to help you if they can't replicate your problem. – hpesoj626 Apr 29 '18 at 23:55

0 Answers0