Published on by JGD
# NPV and IRR on the HP Prime

Now we’re coming, as promised, to the other important financial functions: net present value of a cash flow list, and the internal return rate of that list of cash flows. I will not discuss these since this is not the place; suffice to say that these are the main indicators in most advanced financial environments to decide upon investments, write-offs, impairments and other important things.

These are usually calculated in a spreadsheet, based on detailed income and expense models; but there are many occasions when you’re in a meeting and you are confronted with an easy cashflow of, say, 10 years, and you want to know if it surpasses the investment hurdle for you company (find out its net present value (NPV) at a given comparative discount rate), or just want to know what’s the inner profitability of that investment over the duration of the cash flows (internal return rate, or IRR). You don't have you computer opened, and no one would wait for you to have it opened! You’re the financial guy in that meeting, and you’re supposed to give an straight answer on that profitability on the spot. That has happened to me a number of times, and I have created suitable programs for the HP15c and for the hp41c (both the hp17bII+ and the HP12c come with both as native capabilities; but while he hp17bII is a very convenient implementation, the hp12c is less user friendly because you cannot know if you’re storing the right figures in the right places)

But at the end, with all machines above, you don't have all the cash flows in front of you; you might have entered the wrong number; and, in front of an audience, you want to have full control of the data you’re entering. The graphical machines allow you to see all the cashflows at once, and edit them while seeing all the investment together.

So let's start. First, we need to thank Cyrille de Brévisson, who is the author of these programs (I asked for help when I was not able to get the IRR to work and he replied)

EXPORT NPV(L,R)

BEGIN

SLIST(MAKELIST(L(I)/(1+R)^(I-1),I,1,SIZE(L)));

END;

EXPORT LIST;

EXPORT IRR(L)

BEGIN

LOCAL R;

LIST:=L;

FNROOT(NPV(LIST,R),R,.001,1)*100;

END;

Both functions have to be under the same program name. It works, and it allows the HP Prime (together with the other financial functions it comes with) to be a legitimate financial calculator in its own right! And you can do many more things with it, like explaining the break even point of you company in graphical terms, in an easy way.

Note: I have ordered a Smartstream 410, which is fully compatible with the HP Prime, and some Fourier probes (current, voltage, capacity, temperature). I hope to have the samples by Christmas, and will report about it. It would be the opportunity for every child to have a laboratory on his desk. Fourier offers an extensive range of probes; they are not by any means “professional” in their precision, but the associated cost is far from professional too. Let's see.

Re: NPV and IRR on the HP Prime

Hello

Sorry if this is a totally noob question, but here we go...

I tried to write your code in, but I seem to have a sin tax error on the third line , at the SLIST. Any idea on what can be going wrong?

Thanks a lot

Sorry if this is a totally noob question, but here we go...

I tried to write your code in, but I seem to have a sin tax error on the third line , at the SLIST. Any idea on what can be going wrong?

Thanks a lot

Re: NPV and IRR on the HP Prime

Yes. Due to the impossibility of writing the greek letter Sigma, I wrote an S. If you enter that function from the menus, you will find the right Sigma-list function. Sorry for the delay in replying!

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