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Math and Excel Question (nerd content)

Lord Pmann

Lord Pmann

Lord
Joined
Mar 12, 2012
Posts
19,699
I know there are some fellow nerds here as I have seen you in the Math thread. I have a question that I am not easily finding the answer to.

It is possible to plot non-linear equations in Excel? Like, on a graph? It's logarithmic in nature, not just mx+b. I suppose I can do a scatter chart.

I can post the equation in a bit but it's long and cumbersome.

I thought I'd ask here because I know there are some math brains in our midst. No one here at work can figure it and I'm not an Excel wizard with graphs.

Thanks in advance and I'll post the equation shortly. I realize this is a long shot.
 
I'm only aware of adding a trend line for existing data points. You right click on one of the data points one the chart, and select the Trend/Regression type. I suppose you could define a trend line, and then change the data points to something that would be invisible.
 
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My calculator doesn't even like the equation. :( It has a hard time plotting it and it is a pretty powerful calculator. Excel, from what I see so far is only able to plot data points. It looks like I'm going to have to pick sample points and plot them. :rolleyes: It seems like Excel should be able to plot a two variable system. I don't understand why it can't. I really don't. I can see it having trouble with my particular problem, as it's logarithmic.

Here is the equation:

image_zps30e05a4c.jpg


The unknowns are t and Ibf (that is one variable). I have the letter E in there, but I define that as it changes for my different scenarios. And the log is actually log base 10, not ln (natural log). It's a bitch figuring out how to represent that in Excel.

Thanks for the idea Dr. I'll see what I can get.

And sorry about such an off the wall question. But a lot of people come to this site, so I figure we may have some expertise.
 
Excel is a spreadsheet software.

Trying to do this with Excel is like trying to write a letter with MS Paint. Why would you want this?

Use MatLab for this.
 
Primalex said:
Excel is a spreadsheet software.

Trying to do this with Excel is like trying to write a letter with MS Paint. Why would you want this?

Use MatLab for this.
Click to expand...

I understand. But I do not have Matlab or Mathcad at my fingertips. My old laptop has both, but that thing ate shit long ago.

All I want is a simple plot of the equations. I thought maybe Excel would do this.

But you recommend Paint, huh? As you see, I'm a master of paint.
 
pmann said:
My calculator doesn't even like the equation. :( It has a hard time plotting it and it is a pretty powerful calculator. Excel, from what I see so far is only able to plot data points. It looks like I'm going to have to pick sample points and plot them. :rolleyes: It seems like Excel should be able to plot a two variable system. I don't understand why it can't. I really don't. I can see it having trouble with my particular problem, as it's logarithmic.

Here is the equation:

image_zps30e05a4c.jpg


The unknowns are t and Ibf (that is one variable). I have the letter E in there, but I define that as it changes for my different scenarios. And the log is actually log base 10, not ln (natural log). It's a bitch figuring out how to represent that in Excel.
Click to expand...

If you want to plot a function in base Excel you'll probably need to generate pairs of points, then do an x-y plot and select one of the "connect points with lines" options. However, this addon appears to do what you're after and there's an alternate method here. (Disclaimer: haven't used these myself and can't vouch for them.)

In Excel "Log(x)" will give you the base-ten log of x, "Log(x,y)" will give the base-y log, and "Ln(x)" will give the natural log.

Looking at your equation, you can simplify it further by remembering that log(10^blah) = blah.
 
I was able to get a smooth line plot using the x-y scatter option. I didn't actually plot the equation, but rather a shitload of points in the graph. It's not perfect, but it works well enough. Until I get a chance to look at that other website that Primalex posted. That looks like a powerful tool. (That's what she said)

This Excel sheet will work well enough for upper management types who don't understand this stuff anyway.
 
Rainshine said:
lol Gosh I hated Maths. Especially those questions about trains leaving stations... man... :D
Click to expand...

I like how you call it Maths *laughs*.

The train questions weren't interesting. Perhaps if we knew why the train was leaving the station.

"A train full of Playboy models leaves to meet the needs of Hugh Jackman and Christian Bale..."

See? Already more interesting.
 
pmann said:
I like how you call it Maths *laughs*.

The train questions weren't interesting. Perhaps if we knew why the train was leaving the station.

"A train full of Playboy models leaves to meet the needs of Hugh Jackman and Christian Bale..."

See? Already more interesting.
Click to expand...



<<== Foot tappin' stuff, when waiting for a train or finding square roots. You don't always have to show your work ;)
 
Math is always beautiful. It is the language of logic. Not that I'm a math freak, just a lover of math who does math problems to while away the hours.

Excellent job on the previous.

Don't you love Excel? I worked on digicalc too many years ago. For those who wonder, digicalc was the precurser to Lotus 123, which was the precursor to Excel.

It is my believe Microsoft borrowed a lot of the S/W they claimed ownership to over the years. Some they paid well for some they may not have.

Love the old days. Anyone remember punched card programming?
 
Psst... got a punch-card porn? I'd love to see some photos - y'know the real vintage B/W stuff. We have a PC in the lab that has orange lettering!!
 
pmann said:
My calculator doesn't even like the equation. :( It has a hard time plotting it and it is a pretty powerful calculator. Excel, from what I see so far is only able to plot data points. It looks like I'm going to have to pick sample points and plot them. :rolleyes: It seems like Excel should be able to plot a two variable system. I don't understand why it can't. I really don't. I can see it having trouble with my particular problem, as it's logarithmic.

Here is the equation:

image_zps30e05a4c.jpg


The unknowns are t and Ibf (that is one variable). I have the letter E in there, but I define that as it changes for my different scenarios. And the log is actually log base 10, not ln (natural log). It's a bitch figuring out how to represent that in Excel.

Thanks for the idea Dr. I'll see what I can get.

And sorry about such an off the wall question. But a lot of people come to this site, so I figure we may have some expertise.
Click to expand...

Is that the equation for arc flash energy?
 
DvorakAgain said:
Is that the equation for arc flash energy?
Click to expand...

Yes. But there was an error in that. I can't remember where, but I think I did the log incorrectly. It's fixed. And I just, instead of plotting the actual equation, plotted a shitload of points.

Is there another nerd among us???
 
pmann said:
My calculator doesn't even like the equation. :( It has a hard time plotting it and it is a pretty powerful calculator. Excel, from what I see so far is only able to plot data points. It looks like I'm going to have to pick sample points and plot them. :rolleyes: It seems like Excel should be able to plot a two variable system. I don't understand why it can't. I really don't. I can see it having trouble with my particular problem, as it's logarithmic.

Here is the equation:

image_zps30e05a4c.jpg


The unknowns are t and Ibf (that is one variable). I have the letter E in there, but I define that as it changes for my different scenarios. And the log is actually log base 10, not ln (natural log). It's a bitch figuring out how to represent that in Excel.

Thanks for the idea Dr. I'll see what I can get.

And sorry about such an off the wall question. But a lot of people come to this site, so I figure we may have some expertise.
Click to expand...
*eyes glazed over*

Train questions are easy. It doesn't matter what time they'll collide; there's going to be a lot of dead people and one hell of a mess to clean up. :D

Oh, I beg to differ, but the answer is always 49. :D
 
Btw, if you don't want to pay for a new copy of Matlab, get Octave. It's free and almost identical to Matlab, except that it does not have some of the more specialized toolboxes.
 
You might try CurveExpert, which is a shareware curve fitting program. I haven't used it in years, but it was handy for stuff that Excel wouldn't do and for which I didn't feel like writing programs, such as fitting data to various types of logistic & power functions. I believe the basic version is $45 after the 30-day evaluation period.

"CurveExpert Basic is a comprehensive curve fitting system for Windows. XY data can be modelled using a toolbox of linear regression models, nonlinear regression models, interpolation, or splines. CurveExpert Basic was designed to be simple but powerful, so that all users can obtain a model for their data quickly and easily. Over 30 models are built-in, but custom regression models may also be defined by the user. Full-featured graphing capability allows thorough examination of the curve fit. The process of finding the best fit can be automated by letting CurveExpert compare your data to each model to choose the best curve."

EDIT: Now that I think about it, you wanted to plot a formula, not fit data. You may be able to do that with this program but I can't swear to it.
 
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