Spreadsheets: LibreOffice Calc: how to get a graph and equation from data

The tutor shows how to get a graph and equation for data using LibreOffice Calc, in six easy steps.

  1. Let’s imagine your x-data is in a1:a5, your y-data, b1:b5.
  2. Select the range a1:b5.
  3. Click the Chart icon, which looks like a little pie graph. You’ll probably see your chart immediately, but it may not be a scatter plot.
  4. A chart wizard opens up, offering you choices. Pick XY(Scatter). You can also pick, on successive screens, other options as well, but for this purpose, you can next click Finish.
  5. Now, on the scatter plot that appears, you’ll see blue markers. Click on one of them; they’ll turn green. They need to be green.
  6. Go to the top and click Insert, then the Trend Lines… option. You’ll see different types of equations available. Select the one you desire, then, to see the equation, check the box Show Equation. Finally, click OK.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Navigating the file system from the terminal (aka Command Prompt): how to enter a two-or-more word directory or file name

The tutor shares a hint he noticed recently.

When I started with computers, I don’t believe you could have a folder name like this folder: as I recall, you couldn’t have a space in the name. (You could have an underscore as in this_folder).

I don’t know for sure, but I’d say Windows opened up the possibility of having a space in the name of a folder (or file). Nowadays, on people’s desktops, you commonly see folders with two-or-more word names, such as Road Trip Summer 2016 or Kitchen Reno. (I wonder if anyone else realizes what computer users seem to take for granted:)

On the desktop, two-word names don’t matter: you can just double-click the folder to open it. In the terminal, though, you need to type the folder (aka directory) name to enter it. Will the terminal know what you mean when you type a folder name that contains a space?

The terminal (aka, Command Prompt) in Windows 7 does understand a two-word name. For instance, if you want to enter the Kitchen Reno directory, just typing

cd Kitchen Reno

will work.

In the Linux terminal, from my experience, the command

cd Kitchen Reno

won’t work. However, you’ve got two options that will:

  1. cd “Kitchen Reno”
  2. cd Kitchen\ Reno


cd “Kitchen Reno”

works in both Windows 7 and Linux:)

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Web design: css3 gradient, part III: browser support

Continuing about css3 gradient effects, the tutor discusses some of the browsers that do or don’t support them.

In my previous two posts (here and here), I’ve been talking about the css3 gradient effect. I’ve acknowledged that not everyone viewing those posts can see the effects, but I continue to believe that most people can.

On my ancient 32-bit system, which runs under Linux (Ubuntu), the gradients show up on Firefox. (It’s the browser that came with Ubuntu.)

My equally ancient 32-bit Windows XP system (from 2002) has two browsers: ie8 and Opera. As I expected, ie8 doesn’t show the gradient effects at all. Opera, however, shows them perfectly.

My wife has a Mac with Safari; the gradient effects show up fine on it.

Finally, we have two Windows 7 computers, both of which have Chrome and ie11. The gradients all show up perfectly on Chrome. On ie11, the middle rectangle’s gradient (from top left to bottom right) does not show up, but the other two do.

In future posts I’ll discuss browser usage:)

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Linux: display ls results one page at a time

The tutor tells a useful hint he learned from unix.com.

Sometimes, searching a directory in Linux, the results are so numerous that the user is plunged to the end, not being able to see the early or middle entries.

There is a way to avoid this: apparently, the command


displays just the first page of the search results. To see the rest, the command

x d

advances the list by x entries.

On my system, anyway,

x Space Bar


x Enter

will also advance the list by x entries.

Another option is


after which you can arrow up or down though the list.

To quit out of the list, press q




Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

External drives: finding unrecognized space (or perhaps even a drive itself)

The tutor continues talking about the usb hard drive he bought perhaps six years ago.

Back in my Oct 27 post I described a peripheral hard drive bought around 2009, mentioning it was about $50 at the time, and stored about 60Gb.

I said 60Gb because when I plugged it into the Windows 7 computer, it recognized 60Gb in two partitions. However, I recalled the drive’s capacity actually being much larger – 500Gb. I decided I’d just remembered wrong.

Looking around for my drive on the net, though, I often encountered articles about not being able to find usb storage that is plugged in. I came to wonder if, somehow, those articles applied to me. Was the lion’s share of my external drive’s capacity simply not being recognized by Windows?

I clicked one of the articles and learned about a Windows feature called Disk Management, which can be opened from the search box in the Start menu. Doing so, I saw that, indeed, the external drive is 500Gb.

When I first got the drive, I partitioned it using Linux. Perhaps the file formatting I used for some partitions is not recognized by Windows. About 325Gb I suppose I left raw; the Disk Management table shows it as Unallocated.

Here’s the article.


Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Easter eggs: the factor command

Here, the tutor is happy to report, Easter comes early.

An easter egg is a feature not reported. To become aware of it, the user must either stumble upon it, or else find out from research.

Reading about Linux terminal commands, I’ve recently become aware of the factor command. For example,

factor 24

will yield its prime factorization as follows:

24: 2 2 2 3

(Of course, 24=2x2x2x3.)

The command works identically from the Windows command prompt, even though when you type help, the factor command is absent from the list.

Neat, huh?


McGrath, Mike. Linux in easy steps. Southam: Computer Step, 2008.

Wikipedia (easter egg)

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Linux: ls command: listing subdirectories first, part II

The tutor talks more about listing subdirectories first with the Linux ls command.

I began with this topic in my May 17 post (exactly five months ago, I notice:) While the solution therein is very helpful, I’ve found another one that might be even simpler:

ls -X

Linux is case sensitive; the capital X switch means the directory contents will be listed by the alphabetical order of the file extensions. In my experience, directories don’t have file extensions, whereas files usually do (or should). From the point of view of alphabetical order, the items with no file extension are listed before those that have. Therefore, the subdirectories are generally listed first, unless files have been named without extensions.

For me, ls -X seems to work pretty well to list the subdirectories first.




Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Linux: terminal: listing subdirectories (directories) only

The tutor shares a nice tip that he finds very helpful:  listing the subdirectories only with the ls command.

I write a lot of little programs to test built-in functions or show examples of their use.  Of course, as they accumulate, organizing them becomes important.

Before reading further, an important relationship to keep in mind is that a directory is to the terminal what a folder is to the desktop. A subdirectory, then, is like a folder within a folder. I use both file environments, so I use the terms directory and folder interchangeably.

Very often, I’ll store a day’s work in a folder labeled that date, within another folder for the project to which it belongs or what have you.  Returning weeks later, I need to know, from an upper directory, where the folder (aka subdirectory) of a particular date might be.

While there are several ways to find out, I like ls because it’s quick and minimal -especially if you know how to tailor it. The good people at stackoverflow.com offer the variation

ls -d */

as the way to return the subdirectories only.

But what if you want (like me) to know how deep the structure goes?

You can check for second-level subdirectories thus:

ls -d */*/

or third-level thus:

ls -d */*/*/

You can also do simultaneous checks:

ls -d */ */*/

reveals the subdirectories in the current one, as well as the ones they contain.

There might be better ways to search around, but for my purposes these variations of ls work great.


Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Linux: terminal: navigating to a USB drive

The tutor gives a few hints about navigating a USB drive from the Linux terminal.

I’m no Linux expert, but I can find my way around well enough. Remembering that a directory is analogous to a folder, I mainly use

pwd shows where you are (print working directory)

ls shows the files and other directories within your present one

cd .. backs you up one level (cd for change directory)

cd directory_name places you in that directory

The potential problem with a USB drive: do you know where it is (or what it’s called)?

When I plug in a USB, I can find it in the media directory, visible from the top level directory. However, when I invoke the terminal, it doesn’t put me at the top level directory but rather at my home directory. I have to back up a couple of levels to reach the top directory. From there, I can enter ls, then see the media directory among the listings.

The media directory can then be entered:

cd media

Checking its contents thus:


you might see a list of users rather than the USB drive itself. Entering your own directory

cd my_user_name

you might then list its contents


to find the USB drive. The computer might give it a name based on its model number rather than a recognizable handle. You can enter it to confirm it’s the device you’re expecting.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Linux: Ubuntu: aplay and arecord

The tutor shares some discoveries he made while producing a sound file.

In my Feb 2 post I mentioned that the bell (‘\a’) is apparently disabled in my flavour of Ubuntu (14.04). Yet, I want a bell-like sound for an upcoming experiment.

Today, I decided to create a little “bell sound” file which will be played by Perl’s exec function. (Once again: my Feb 2 post for details.)

From man aplay I learned about the arecord function. From the terminal I keyed in

arecord sounds/beep0.wav

then the terminal would message back that recording had started. I’d make the “bell” noise for around ten seconds, then kill the process with Ctrl+c. Next I’d key in

aplay sounds/beep0.wav

to hear the result.

While the laptop had a built-in microphone, I also had two old headsets that each had one. The jack one didn’t work, but the USB one did, and conveyed a nice clear recording.

To make the actual sound, I didn’t have a bell. I settled on clinking a spoon against a large coffee cup.

Everything seemed to work out fine; I’ll share the implementation soon:)

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.