IRR Error Message

Things that aren't right, that are in the queue to be fixed... along with workarounds.
RaySammartino
Posts: 11
Joined: Sat Aug 09, 2008 5:05 am

IRR Error Message

Post by RaySammartino » Sun Nov 09, 2008 1:32 pm

I have entered the following cash flow into the calculator:
100,000 [CHS],
[blue] CFo (this equals -100,000)
50,000 [blue] CFj
25,000 [blue] CFj
4 [blue] NJ
10,000 CHS (this equals - 10,000)
[blue] CFj
[gold] irr

and I get the following error message "Check Cash Flows only 1 sign change allowed"

Why is this happening? This is a fairly standard calculation for financial analysis IRR's (positive and negative cash flows).
Please advise.
Thanks,
Ray Sammartino

theDev
Posts: 240
Joined: Mon Aug 04, 2008 8:58 pm

Re: IRR Error Message

Post by theDev » Sun Nov 09, 2008 11:18 pm

Ray:

Let me check with the math wiz... for the most part, problems with more than one sign change can have more than one root -- meaning that there is more than one mathematical answer. And which one is correct can be anyone's guess because they're both correct but only one is the one you are looking for.

But let me see if Roy can work this one out. He's pretty darn smart!!!

Kim

Xeno
Posts: 55
Joined: Sat Oct 25, 2008 4:15 pm

Re: IRR Error Message

Post by Xeno » Mon Nov 10, 2008 12:12 am

What's the problem, please? :)

It works for me.

15.63% was the answer given to me by Calc 12E, verified on an HP 17B

RaySammartino
Posts: 11
Joined: Sat Aug 09, 2008 5:05 am

Re: IRR Error Message

Post by RaySammartino » Mon Nov 10, 2008 4:22 am

It doesn't work for me when the first cash flow is entered into CFo. But I found last night that it does work if the first cash flow is entered into CFj. The CFo first cash flow entry is what I have always used in my HP (supposed to replicate cash flow "0").

Xeno
Posts: 55
Joined: Sat Oct 25, 2008 4:15 pm

Re: IRR Error Message

Post by Xeno » Mon Nov 10, 2008 2:49 pm

Hi Ray,
To make sure I am not making a mistake entering the problem, here are my exact keystrokes:
g TVM
f FIN
100000 CHS g CFo
50000 g CFj
25000 g CFj
4 g Nj
10000 CHS g CFj
f IRR

= 15.633

I tried clearing the registers again and, ignoring CFo, entering the -100K into CFj but I got -11.200 as the result instead.

This is not consistent with your results so at this point I suggest the usual set of baselining actions:
- Check for updates on iTunes
- Reboot the iPhone
- Delete and reload Calc 12E on your phone

Just two days ago I had Safari seemingly working but acting really weirdly and could not get it to behave until I rebooted the phone, so this might work for you.

Please let us know if I have the problem wrong or what other progress there is, but I have tried this on two separate iPhones using Calc 12E and both of them are working correctly as above. Good luck.

RaySammartino
Posts: 11
Joined: Sat Aug 09, 2008 5:05 am

Re: IRR Error Message

Post by RaySammartino » Tue Nov 11, 2008 10:44 am

Ok...these are my exact key strokes:

(END of period calc's)
g TVM
f FIN
100,000 [CHS],
[g] CFo (this equals -100,000)
then...
50,000 [g] CFj
25,000 [g] CFj
4 [g] NJ
10,000 CHS (this equals - 10,000)
[g] CFj
[f] irr
Error Message: "check cash flows, only one sign change allowed"

When I enter the first cash flow as :
100,000 [CHS]
g CFj
(and the rest the same as above)
I get the correct answer: 15.63299

I checked this on my HP 12C and with three other HP 12C's in my office. All get the same answer: 15.63299. In NO case did we get a - 11.2 !! Prior to doing this I re-booted the phone (not Reset), deleted and re-installed the program. Is this because the program is the 12E and not the 12C? I thought the app that I originally downloaded was a replication of the 12C. Did this change? Interestingly, the HP 12C doesnt have a TVM key!

Thanks for your patience.
- Ray

Xeno
Posts: 55
Joined: Sat Oct 25, 2008 4:15 pm

Re: IRR Error Message

Post by Xeno » Tue Nov 11, 2008 1:02 pm

It is a mystery. Same keystrokes, same product, same phone but I get right answers and you cop wrong ones. :?

The HP 17B II gets 15.63% regardless of whether you make the -100K entry at CFo or leave that entry as zero and make all the entries numbered. Nor can I get a wrong answer from Calc 12E, no matter how hard I try. When I got -11.2, when entering zero in CFj, I had switched the sign on an entry, so with correct keystrokes that is now correct too, same as the HP 12C and 17B.

The fact that Calc 12E has a TVM key is a convenience and not a meaningful change from 12C operation, so that is not the source of the problem.

Ray and I are at an impasse. There is no point he and I saying "yes it does" - "no it doesn't" at each other. Would someone else please test this and let us know what happens to them?

I just very carefully did it all again, twice, and still get the right answers! Setting the flows to beginning or end of period made no difference to the IRR.

RaySammartino
Posts: 11
Joined: Sat Aug 09, 2008 5:05 am

Re: IRR Error Message

Post by RaySammartino » Tue Nov 11, 2008 3:59 pm

Some more food for thought. I went to my home computer and did the same run as you suggested (which I did at my office) that is: deleted the program from my phone, re-boot phone, then re-download the program from my home computer. The program on my home computer was the prior version of Calc 12 (version 2.0.0)...and it works perfectly! Then my Iphone indicated that an update was available, so I decided to see what happens when I download and run it on the phone. So, I downloaded the app (via the phone) and ran it, but I now get the same error! So, maybe there is something about the new update Version (2.1.0). Hope this leads to a solution!
Thanks,
Ray

Xeno
Posts: 55
Joined: Sat Oct 25, 2008 4:15 pm

Re: IRR Error Message

Post by Xeno » Tue Nov 11, 2008 4:29 pm

Ah, now that gets interesting!

I bought Calc-12E (not 12C) on 24 October, and its version number is 1.0.0.

I believe that owners of the prior Calc-12C were upgraded automatically to 12E, but this involved creating a new version of 12C on the iTunes store to get around Apple's licensing process. Perhaps this was not seamless? Kim?

theDev
Posts: 240
Joined: Mon Aug 04, 2008 8:58 pm

Re: IRR Error Message

Post by theDev » Wed Nov 12, 2008 10:44 am

Not seamless. Quite a hassle really. In order to provide updates to existing customers I have to maintain the original app on the store, and it HAS to have versioning consistent with what it was doing -- I can't take it backwards to v1.x to match Calc-12E. I had to hold updating Calc-12E (to 1.1.0) because I needed to get translations for foreign iTunes stores so the two got out of sync... Calculator12 got updated, and E is still held). It's not a licensing thing, it's a naming thing that they're very picky about--rightfully so I might add!

So: Calculator12 v2.1.0 added a sign check to IRR that was not there before, this is because of the multiple root problem mentioned above. The test case that exposed the issue is one that has two complex roots, and HP returns answers that are totally wrong:

Cf0 = 1000
Cf1 = -2000
Cf2 = 1500

Locks the calculator which is a very very very bad result. Hence the sign change check in v2.1.0. Ray's note from 11/11 10:44A indicates that he's running Calculator12 v2.1.0 -- and the cash flow sign error is the designed behavior. Note that Calc-12E v1.0.0 and Calculator12 v2.0.0 do not generate an error for multiple roots and will attempt to solve Ray's initial problem, so they won't give you an error message but they might give you a wrong answer or worse yet lock up.

I need to check with Roy on this one -- the HP devices warn you about the possibility of bogus roots being found, and then they go ahead and try to solve the problem which sometimes means the "solution" is nonsense. Roy and I really didn't want the potential of "wrong" answers being presented at all so we refuse to attempt solutions of multiple root problems... Maybe we should have a "solve anyway, I know the answer might be bogus" button for you to press if you want to live dangerously?

Kim

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