"Warning: Excess Cash Flows Have Been Discarded"

Things that aren't right, that are in the queue to be fixed... along with workarounds.
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jon20009
Posts: 10
Joined: Sat Jan 17, 2009 11:54 pm

"Warning: Excess Cash Flows Have Been Discarded"

Post by jon20009 » Sun Jan 18, 2009 12:09 am

I think on an actual HP12C there are some 20 registers?

And I can store any whole number from 0 up to and including 99 into Nj. So one can computer a stream of cash flows much larger than 99 by storing the flows in more than one register. Innstead of inputing 10 Cj 150 Nj, which would produce an error one could input 10 Cj 99 Nj 10 Cj 51 Nj.

(1) The problem is when I input any number of cash flows greater than 99 on the iPhone 12E calculator (even when splitting them into more than one Nj) and I check the visual cash flow display it says "excess cash flows have been discarded" ? It only displays 99 cash flows.

What is happening? Can the 12E simply not display in the visual cash flow window more than 99 cash flows but the calculation of NPV is using all the cash flows or are the cash flows after the 99th actually being discarded from the NPV calculation ?

(2) When I open the visual cash flows window when using TVM (n, i, PV, PMT, FV) problems the cash flows don't seem to make sense. Does the visual display only work for NPV (Cj Nj) problems ?

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

Re: "Warning: Excess Cash Flows Have Been Discarded"

Post by theDev » Sun Jan 18, 2009 7:53 am

There are two (or three?) questions here... I think!

First: more than 99 cash flows total. I chose to limit the visual cash flow viewer to 99 total cash flows for two reasons, neither of which is cast in stone. First, as you might notice, it takes about a second or so for the cash flow viewer to appear when there are 99 cash flows, this is because it just takes a while to draw. Taking second or so seemed to be ok for me, the delay didn't make me wonder about the calculator possibly having locked up or something. That can be taken care of with the little spinning thing or some other notation but. 'The bigger reason is that I didn't think that folks routinely use more than 99 cash flows but I didn't ask so I could be wrong. BTW, computing IRR for 99 cash flows takes a while and there isn't a spinney wait indicator so if you do try it be patient! What is happening is that when you bring up the cash flow editor it literally ignores cash flows that are greater than 99 and will NOT use them to compute IRR, NPV or MIRR. Not only that, but it also adjusts the Nj portion of the last cash flow entry as well, so once the viewer is invoked it really and truly discards the tail end. If you don't bring up the viewer, I don't check or otherwise disturb the Nj entries.

Second (sort of question): yes, you are limited to 20 different cash flow groups, just like the HP. Again, this was done without asking and certainly can be expanded if having more than 20 cash flows are useful.

Third question: no cash flow viewer in TVM. This is correct, the cash flow viewer does not display TVM problems. When you invoke the cash flow viewer it shows you the stuff you have entered using CFo and CFj, not your TVM problem, and the display of the CFo/CFj problem may be "wrong" because it assumes that the value in the n register is how many cash flow groups have been entered. If you changed n for your TVM problem it no longer represents the number of cash flow groups. I did this because I can't tell what you were interested in, a view of the TVM problem or perhaps of a previously entered NPV problem--they coexist with the exception of the n register. So I chose to display the NPV stuff since until now you simply couldn't see it without lots of keystrokes.

So I am very interested in your feedback: is it USEFUL (technically, it is of course doable) to have more than 99 cash flows? and in a similar vein, is it USEFUL to be able to visualize a TVM problem using the cash flow diagram? I stress useful because curious feats of amazing programming prowess are nice, but if they don't actually help people solve real problems they're a fun intellectual exercise but not much more.

How do you like the viewer/editor by the way?

Kim

jon20009
Posts: 10
Joined: Sat Jan 17, 2009 11:54 pm

Re: "Warning: Excess Cash Flows Have Been Discarded"

Post by jon20009 » Mon Jan 19, 2009 2:14 am

Thank you for your responsiveness. It's very impressive.

"How do you like the viewer/editor by the way?"

I'll start with this. I love it.

This visual display/editor of the cash flows feature along with display of the stack and fin register values are the prime reasons I purchased the product despite already owning the Thomas Fors 12C product, which is a superb emulation of the 12C down to the shape and look of the keys.

"The bigger reason is that I didn't think that folks routinely use more than 99 cash flows but I didn't ask so I could be wrong. BTW, computing IRR for 99 cash flows takes a while and there isn't a spinney wait indicator so if you do try it be patient! "

It's not great that the 12E has, in this regard, less functionality than the actual 12C. By way of contrast, the Thomas Fors 12C can handle more than 99 cash flows (I believe 99 per register just like the physical 12C. ) There are problems in which more than 99 cash flows are desirable. For example, take a look at the HP12c solutions handbook under "wrap-around mortgage" example 2.

http://www.scribd.com/doc/7405475/HP-12 ... s-Handbook


"What is happening is that when you bring up the cash flow editor it literally ignores cash flows that are greater than 99 and will NOT use them to compute IRR, NPV or MIRR. Not only that, but it also adjusts the Nj portion of the last cash flow entry as well, so once the viewer is invoked it really and truly discards the tail end. If you don't bring up the viewer, I don't check or otherwise disturb the Nj entries."

I don't like this behavior of changing the problem on someone from what they want computed to something else. If one did input more than 99 cash flows (which if I understand you can be computed on the 12E so long as you don't enter the visual editor), I can't see that someone would actually want this alternative cash flow problem forced on them by the 99 limit to be solved.

The 12E should either be able to solve the problem you want solved or it should tell you it can't do it. Truncating the cash flows to the first 99 is the worst of both worlds. It doesn't solve the problem you wish solved and it returns an answer to a problem you didn't enter and presumably don't want solved. The message shouldn't say "excess cash flows discarded" it should say "the visual editor can not be used for cash flow problems with more than 99 cash flows".

And even if it is going to solve this 99 cash flow problem of questionable interest, I don't think the message actually presented makes it clear what is happening. I wasn't sure if you just discarded the cash flows for purposes of the display or, as you explained in your reply, discarded them in the calculation.

Another problem with this behavior of truncated cash flows to 99 is that if you do the calculation one way (without going into the cash flow editor) it will work but if you do it another (by entering the cash flow editor to even look at the problem) you get another answer.

But after thinking about it some more I understand the issue with having a cash flow visual that goes on past 99. It's too long. Perhaps for problems involving cash flows beyond 99, the post-99 cash flows could be collapsed somehow. And expanded when you click a particular Cj value.

Or alternatively, have an accurate message and compute the answer to the problem that was input. Say something like "cash flows beyond the 99th are not displayed in the editor but are used to compute the result" and use ALL the cash flows to give the correct answer instead of solving a problem the user didn't input.

"Second (sort of question): yes, you are limited to 20 different cash flow groups, just like the HP. Again, this was done without asking and certainly can be expanded if having more than 20 cash flows are useful."

20 different cash flow groups seems sufficient.

"Third question: no cash flow viewer in TVM. This is correct, ...."

Got it. Do you have any plans to do a traditional user guide ?

I also wanted to note a behavior I discovered when doing IRR problems.

Your product is faster then my actual 12C when it comes to computing IRR with a small number of cash flows but it is significantly slower when it comes to a long series of cash flows. For example, if you key in this: -10 CF0 10 CFj 80 Nj and then function IRR, it takes the actual 12C around 30 seconds. It takes the 12E more than 1 minute. It takes the Thomas Fors 12C emulation 10 seconds. Thank you for your responsiveness. It's very impressive.

"How do you like the viewer/editor by the way?"

I'll start with this. I love it.

This visual display of the cash flows feature along with display of the stack and fin register values are the prime reasons I purchased the product even though I have the Thomas Fors 12C product, which is a superb emulation of the 12C down to the shape and look of the keys.

"The bigger reason is that I didn't think that folks routinely use more than 99 cash flows but I didn't ask so I could be wrong. BTW, computing IRR for 99 cash flows takes a while and there isn't a spinney wait indicator so if you do try it be patient! "

It's not great that the 12E has less functionality than the actual 12C. By way of contrast, the Thomas Fors 12C can handle more than 99 cash flows (I believe 99 per register just like the physical 12C. ) There are problems in which more than 99 cash flows are desirable. For example, take a look at the HP12c solutions handbook under "wrap-around mortgage" example 2.

http://www.scribd.com/doc/7405475/HP-12 ... s-Handbook


"What is happening is that when you bring up the cash flow editor it literally ignores cash flows that are greater than 99 and will NOT use them to compute IRR, NPV or MIRR. Not only that, but it also adjusts the Nj portion of the last cash flow entry as well, so once the viewer is invoked it really and truly discards the tail end. If you don't bring up the viewer, I don't check or otherwise disturb the Nj entries."

I don't like this behavior of changing the problem on someone from what they want computed to something else. If one did input more than 99 cash flows (which if I understand you can be computerd on the 12E so long as you don't enter the visual editor), I can't see that someone would actually want the alternative cash flow problem forced on them by the 99 limit to be solved.

The 12E should either be able to solve the problem you want solved or it should tell you it can't do it. Truncating the cash flows to the first 99 is the worst of both worlds. It doesn't solve the problem you wish solved and it returns an answer to a problem you didn't enter and don't want solved. The message shouldn't say "excess cash flows discarded" it should say "the visual editor can not be used for cash flow problems with more than 99 cash flows".

And even if it is going to solve this 99 cash flow problem of questionable interest, I don't think the message actualy presented makes it clear what is happening. I wasn't sure if you just discarded the cash flows for purposes of the display or, as you explained in your reply, discarded them in the calculation.

Another problem with this behavior of truncated cash flows to 99 is that if you do the calculation one way (without going into the cash flow editor) it will work but if you do it another (by entering the cash flow editor to even look at the problem) you get another answer.

But after thinking about it some more I understand the issue with having a cash flow visual that goes on past 99. It's too long. Perhaps for problems involving cash flows beyond 99 you could present a display which collapses the different CFj values. And each could be expanded and the individual cash flow values modified as desired.

Or alternatively, have an accurate message and compute the answer to the problem that was input. Say something like "cash flows beyond the 99th are not displayed in the editor but are used to compute the result" and use ALL the cash flows to give the correct answer instead of solving a problem the user didn't input?

"Second (sort of question): yes, you are limited to 20 different cash flow groups, just like the HP. Again, this was done without asking and certainly can be expanded if having more than 20 cash flows are useful."

20 different cash flow groups seems sufficient.

"Third question: no cash flow viewer in TVM. This is correct, ...."

Got it. Do you have any plans to do a traditional user guide ?

I also wanted to note a behavior I discovered when doing IRR problems.

Your product is faster then my actual 12C when it comes to a small number of cash flows but it is significantly slower when it comes to a long series of cash flows. For example, if you key in this: -10 CF0 10 CFj 80 Nj and then function IRR, it takes the actual 12C around 30 seconds. It takes the 12E more than 1 minute. It takes the Thomas Fors 12C emulation 10 seconds. That TF 12C emulation is much faster when computing any IRR problem but especially with large numbers of cash flows.

I'm not sure why the 12E is so slow with large numbers of cash flows but it would be VERY helpful to have some indication that the product is still working. Sometimes I think the program has frozen. The Thomas Fors 12C product flashes "running", just like the actual 12C does so you know it's working.

You mentioned in the context of the generation of the cash flow diagram that "That can be taken care of with the little spinning thing or some other notation... " Having some indication that the 12E is working during the IRR calculation would be great.

Thank you for consideration of my comments. And good luck with your product. :!:

jon20009
Posts: 10
Joined: Sat Jan 17, 2009 11:54 pm

Re: "Warning: Excess Cash Flows Have Been Discarded"

Post by jon20009 » Mon Jan 19, 2009 2:22 am

Sorry my answer was duplicated.

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

Re: "Warning: Excess Cash Flows Have Been Discarded"

Post by theDev » Mon Jan 19, 2009 7:38 am

No problem... and thank you for your explaination--you make a very strong set of arguments and I will "correct" Calc-12E accordingly. I will have to look into why it takes so long to do IRR with lots of cash flows, that's actually something that I had not tested so I need to find out why it is taking so long. It shouldn't!

So on the list: make IRR for large numbers of cash flows faster, then stop the truncation thing (easy).
Last edited by theDev on Mon Jan 19, 2009 9:00 pm, edited 1 time in total.

jon20009
Posts: 10
Joined: Sat Jan 17, 2009 11:54 pm

Re: "Warning: Excess Cash Flows Have Been Discarded"

Post by jon20009 » Mon Jan 19, 2009 3:49 pm

And maybe add when computing "the little spinning thing or some other notation..." that you referred to so one doesn't think the program has frozen during an IRR computation.

Thanks again.

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

Re: "Warning: Excess Cash Flows Have Been Discarded"

Post by theDev » Mon Jan 19, 2009 9:01 pm

check! spinney thing or progress bar or something. Of course, the calculation should be blisteringly fast so I have to get to the bottom of that.

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