# Free or cheap app for log plots

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• epenguin
In summary, the conversation revolves around finding a suitable graphing app to plot log f(x) against log x, with variable step sizes and parametric plotting options. Various apps, including Free Graphing Calculator, Quick Graph, and Wolfram Alpha, are discussed, with recommendations for Excel or a MATLAB clone like freemat.org. The individual was able to solve their problem by adjusting their function and may look for a parametric plotter in the future.
epenguin
Homework Helper
Gold Member
Trying to complete some homework help I got a bit stuck on an elementary or common problem that was always a bit difficult.

I have a function f(x) and just want to plot log f(x) against log x. This is common in chemistry and biochemistry. It should have been easy.

I have picked up several graphing apps but they would not do it.

In the past when I occasionally needed to do this I managed with making variable 10^x or 10^-x and ugly acrobatics. It would be better to do it by a Parametric plot, and have x = log u, y = log f(u).

Whichever way you do it the trouble is the great variation in the step size. At least I think that is why it is not working. I think I may have got away with it earlier because there was not such variation of x as in my present problem, but now I need to cover at least five orders of magnitude. I think what is happening is my apps are graphing me from log x = 0 to -2 but then the whole range from -2.5 to -6 is smaller than a single step. If I made the step size small enough for that range, then it would take for ever to cover the larger range.

Anyway with the apps I have it is difficult or impossible to control the step size.
I have Free Graphing Calculator by William Jockusch. This does have parametric plotting and does havestep size control - which I found once and can't find again Nice colours. Can only do four graphs but that is okay.
Have Quick Graph. More colours, more graphs, better memory, but does not have parametric that I can see.
Have a Wolfram Alpha app,, I did manage to plot the function using the 10^-x wheeze and it looks exactly as I predict, but has no nice graphics, and I wanted to put two simple (asymptote) lines on it, don't know how and saving is awkward. Did not manage to get Wolfram Alpha log plots or parametric to work at all.

Can you recommend anything? Simple to use, I really don't want to spend much time mastering complicated instructions - or lack of instructions! For the moment this is just for one homework question answer, so can't spend much time, though it will be useful in the future

Excel has log axis graphing capability . Others probably do as well .

You could also look for a MATLAB clone like freemat.org with a few lines of code get a log plot

Matlab:
x=[0:0.1:10]
y=log(x.*x)
plot(x,y)

the log function is a natural log (ie log(e) = 1) and the [0:0.1:10] creates an x array from 0 to 10 in steps of 0.1 and x.*x multiplies each element with itself to get ##x^2##

jedishrfu said:
You could also look for a MATLAB clone like freemat.org with a few lines of code get a log plot
That should be http://freemat.sourceforge.net/

jedishrfu
Thank you all for the advice - I shall look at those when I am more on top of my computer than at this moment.
It is for the moment not necessary after all. I was continually getting graphs for a simple problem that just weren't working out as they were supposed to, and I started explaining it to myself as a problems of step size. In fact it was not due to any such subtleties, I was just not writing the function right on the plotter. In fact after all the best way plot f(y) as function of log y is to let log y = x and plot f(10x) against x. So that simple thing was sorted #8 .

I had actually found that a parametric plot worked for me in Wolfram Alpha, but the figures are not very presentable, so I may be looking for parametric plotter later.

## 1. What is a log plot and why do I need it?

A log plot is a type of graph where the scale of the x or y axis is logarithmic, meaning the distance between each tick mark represents a certain magnitude. This type of plot is useful for visualizing data that spans a wide range of values, as it can compress large numbers and make them easier to compare.

## 2. Are there any free or cheap apps available for creating log plots?

Yes, there are many options available for creating log plots for free or at a low cost. Some popular apps include Microsoft Excel, Google Sheets, and Plotly. Additionally, there are various online tools and software programs that offer log plotting capabilities.

## 3. Can I customize the appearance of my log plot?

Yes, most log plotting apps allow for customization of the appearance of the plot. This can include changing the colors, labels, tick marks, and axes. Some apps may also offer advanced features such as adding trendlines or error bars.

## 4. Is it possible to create a log plot from my own data?

Yes, all log plotting apps allow for users to input their own data and create custom plots. In most cases, the data can be imported from a spreadsheet or entered manually. Some apps may also offer the option to import data from external sources such as online databases.

## 5. Are there any limitations to using a free or cheap app for log plots?

While free or cheap apps can be a great option for creating log plots, they may have limitations compared to more expensive or specialized software. These limitations may include fewer customization options, limited data import capabilities, or a smaller range of supported file formats. It's important to research and compare different apps to find the best fit for your needs.

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