Functions (Help me get an 'A'!)

  • Hi, I'm a nearly complete newbie to Excel, and I was wondering if it is possible to graph exponential functions in Excel or any other common PC application.


    Thanks ahead of time for any help.

  • Yes :bsmile:


    But seriously... ask a fairly general question, you'll get a fairly general answer...


    Have a go & post back with specific queries/problems & you'll find people more than willing to help.

  • OK...
    How would I graph: y=100e^((0.1566678764)x) ?


    Is there some sort of tool where I can define my own function? I looked through the formulas given to me, but none of them seemed to deal with population growth (which is what I'm manipulating). Am I missing something obvious?

  • OK.... right, first i'm no statistician so I can't help on the exact equation (I was terrible at maths - hence i'm an accountant... figure that one out! :lol: )


    But, yes you can create a User Defined Function using VBA...


    Here's an example of one that creates an interest contribution analysis...



    This is placed in a module in the VBA editor (which can be accessed by hitting Alt+F11 whilst in XL and choosing insert|module from the menu)


    What all of the above means is that if you know the account no, the balance & the name of the lookup table, the formula can calculate the amount of profit for the day.. using a set of other formulas as laid out in the code....


    You may want to explore more to see if XL can do it without this as it can get quite complicated & like i said, I'm not statitically mindd enough to know if XL already has that functionality & that I've just never used / found it...


    Hope this helps (even a bit) ;)

  • Hmmm...
    thanks a lot Will, but nothing happens when I press Alt+F11 I have windows 95, so maybe my version is too old. But that sample function seems straightforward enough. I think I could work something out

  • What version of Excel are you using? :no:


    I must admit that I've only used Excel 97 onwards ... prior to that I was a Lotus user, so if you're running XL 95, you may have an issue...


    What happens if you use the macro recorder to record a very simple macro? You should be able to edit the macro code - does this bring up the VB editor.... or maybe someone else knows whether XL 95 was very different to 97...

  • I thought all she wanted to do here was plot an equation?


    Stephen Bullen created a nice chart example that allows you to enter equations as y in terms of x and see it graphed.


    Here's a copy of his spreadsheet.


    Your formula has to be restated slightly in excel in order for it to graph.


    For instance, you'll have to explicitly state e as the value 2.71828182845904


    In Stephen's file you are allowed to express the variable x as simply "x" so your formula might look something like...


    100*2.71828182845904^((47/300)*x)


    Also notice equations in excel never assume a mathematical operator. So, when multiplication is implied you have to insert the * operator.


    (I used 47/300 as an approximation for 0.1566678764 you can substitute it back if you like)

    [SIZE="1"]Sub All_Macros(Optional control As Variant)[/SIZE]

  • Quote

    Originally posted by Denis


    Couldn't you just use EXP(1)?


    Yeah, good point. I don't use e too much and hadn't really thought it through all the way...


    I guess in practical application I'd probably just go ahead and assign that formula to the defined name "e" and use that in the formula. For cretins like myself I wouldn't immediatly recognize EXP(1) as "e" but, for those who use it more frequently, sure.

    [SIZE="1"]Sub All_Macros(Optional control As Variant)[/SIZE]

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