## 378 Reputation

17 years, 18 days

## sorry acer -...

I just read your message again, and it appears that I had actually stopped reading the first time around when I saw the .83, wondered where you had gotten that number and went directly to maple to figure it out. After writing my last message, I went back and read yours again and it occurred to me that you had pretty much already explained it. Sorry for the confusion I may have created.

## sorry acer -...

I just read your message again, and it appears that I had actually stopped reading the first time around when I saw the .83, wondered where you had gotten that number and went directly to maple to figure it out. After writing my last message, I went back and read yours again and it occurred to me that you had pretty much already explained it. Sorry for the confusion I may have created.

## related - sort of...

Acer, I was wondering how you came up with the .83 and .81 so I did a 3d plot and saw a minima around .78, so I then did:
Minimize(x^3-3*x*y+2*y^2-3*x+4*y+3, x = -.1 .. 2, y = -1.1 .. 1,location=false)
and got   [.789062499999999998], indicating that the contour line would never cross that point since it was indeed the minima.

I then redid the contourplot with [.79] eliminated the point at [0,-1], zoomed in, and observed the dot was actually surrounded by the contour line. I was wondering if there is an easier way to go about this. What I did to get from point A to B, seemed a little weird.

## related - sort of...

Acer, I was wondering how you came up with the .83 and .81 so I did a 3d plot and saw a minima around .78, so I then did:
Minimize(x^3-3*x*y+2*y^2-3*x+4*y+3, x = -.1 .. 2, y = -1.1 .. 1,location=false)
and got   [.789062499999999998], indicating that the contour line would never cross that point since it was indeed the minima.

I then redid the contourplot with [.79] eliminated the point at [0,-1], zoomed in, and observed the dot was actually surrounded by the contour line. I was wondering if there is an easier way to go about this. What I did to get from point A to B, seemed a little weird.

## not sure -...

I was thinking I had passed a pointer of mixed data types from maple to C once before, but if I did, I can't find it, and can't remember how to do it. I just tried it with an array of mixed types, and although an array of same types works fine, the mixed type didn't work. It would be nice if one could pass a pointer to anything and then just unscramble it in the C, but I'm not sure how to do that with Maple.

One workaround until someone gives a better idea, is to array each of the data types and then pass the arrays. For example, if you have 15 integers, 12 floats, and 2 strings, array each and then pass the 3 arrays in the call.

I'll try to figure out a better way if I find time later today. Hopefully, before then, somone else will come up with a good idea.

## not sure -...

I was thinking I had passed a pointer of mixed data types from maple to C once before, but if I did, I can't find it, and can't remember how to do it. I just tried it with an array of mixed types, and although an array of same types works fine, the mixed type didn't work. It would be nice if one could pass a pointer to anything and then just unscramble it in the C, but I'm not sure how to do that with Maple.

One workaround until someone gives a better idea, is to array each of the data types and then pass the arrays. For example, if you have 15 integers, 12 floats, and 2 strings, array each and then pass the 3 arrays in the call.

I'll try to figure out a better way if I find time later today. Hopefully, before then, somone else will come up with a good idea.

## SlideRule Status...

I figured I'd add some links to one of my slide rules that I made for a teacher of gifted 4th and 5th graders, as well as a link to a virtual ruler of the same. After deciding that the lines were kinda hard to keep track of for both his and my own somewhat tired eyes, I figured I'd add a glass cursor - like the slide rules of ancient times had. My cursor, is quite a bit bigger to accommodate that unusual shape of my slide rule.

2timv.com/KidsRule/MarkSlideFront.jpg

2timv.com/KidsRule/MarkSlideZoom.jpg

2timv.com/KidsRule/MarkSlideBack.jpg

2timv.com/KidsRule/MarkVirtualRule/

It looks rather large in the pictures, but it's only about 10". I set the main text on his to "Kidding Around!" at his request, but the usual is "Kid's Rule!" as I mentioned elsewhere in my blog.

Below is a link to the manual. It doesn't look as well as a pdf as the printed and bound copy, but it will at least give you an idea of what I give the kids to get them acquainted with the slide rule.

2timv.com/KidsRule/KidsRuleManual.pdf

## Vectors, Dot Products, Cross Products...

Anyone reading this who is interested in viewing a lecture concerning vectors, and more specifically the dot products and cross products being discussed here, below is a link to a video presented by "MITOPENCOURSEWARE". The professor giving the lecture, does an extraordinary job in all the lectures provided at the site. He uses a lot of visual aids to greatly simplify the understanding of some difficult subjects.

## Vectors, Dot Products, Cross Products...

Anyone reading this who is interested in viewing a lecture concerning vectors, and more specifically the dot products and cross products being discussed here, below is a link to a video presented by "MITOPENCOURSEWARE". The professor giving the lecture, does an extraordinary job in all the lectures provided at the site. He uses a lot of visual aids to greatly simplify the understanding of some difficult subjects.

## the squiggle - Robert (updated)...

You may have missed the idea. The squiggle would not represent numeric data - the drawing of the squiggle would. The movement across the x/y of the touchpad would have created that numeric data.

With that in mind, there are numerous ways to accomplish this. One is simply to have the size of the increase/decrease depend upon the X position and either position or velocity of the Y position. For example at a low positioning of Y and increase in X, there would be an increase in the lower digits. Increasing Y (while still moving along the X axis) would create an exponential increase in the upper digits.

I should have had something to demonstrate before mentioning this, but I just now made a simple application (Windows) giving an idea:

2timv.com/misc/NumChng.zip   ( there is a windows executable within the archive not a maple worksheet )

That application will require the installation of the .NET 2.0 environment to run. If you don't have it and really want to run it, I've created an installation source that installs the .NET environment as well as the application at the link below:

I designated specific regions in an attempt to simplify the example. The rate of increase within any region (not in my example) could be fine tuned by simply holding down a particular keyboard key, so the rate of increase, even at the smallest level, could just creep along. Keep in mind that the number shown could just as easily represent 98.765932, so the rate of increase for the lowest particular digit of interest could require a great deal of movement anyhow. The decimal point location could be placed when finished, so during construction it could be interpretted however you please.

Rather than the method shown in the example, I think a better model would be to draw a plot as the data is created, and then the movement over the pad in a reverse direction could just as easily be made to automatically backstep (undraw the plot) to decrease the value of the numeric data.

The sample is just thrown together, only about half works, is very sloppy, etc, but should be enough to give an idea of what I'm thinking. If anyone is interested in any of this, I can perhaps make a better example and add it to my blog rather than take up too much space within this one.

## I think I understand...

I suppose I'm of the same or at least similar persuasion. One thing I'd like to see, is a more efficient means of entering large numeric data. For example the following little "squiggle", scratched out on a touchpad, could represent the numeric value "98765932" - a lot quicker than punching it out on a keypad. Perhaps, someday it will.

## JacquesC, you may be correct -...

JacquesC, you may be correct, but my preferred method is the mouse.

Most people who assist in this forum also seem to prefer your method of input, however it would seem to me to still be difficult to determine the preferred method by the majority, since it is first difficult to determine what group of people comprise the majority,  and second, there is a relatively small minority of users of all types who actually participate within this forum.

## good explanation...

Doug, I think that was a very good explanation. When I began using Maple, I constantly got snagged by leaving out the multiplication symbol, along with a few other things you mentioned here.

## good explanation...

Doug, I think that was a very good explanation. When I began using Maple, I constantly got snagged by leaving out the multiplication symbol, along with a few other things you mentioned here.

## thanks Robert...

Besides some confusion with the quotes, leaving out the multiplication symbol is perhaps the mistake I most frequently make.
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