Carl Love

## 26386 Reputation

11 years, 141 days
Himself
Wayland, Massachusetts, United States
My name was formerly Carl Devore.

## "Higher degree" poly is already factored...

@adel-00 Of course your higher-degree polynomial can be solved; it is already factored into factors of degree less than 5. Finding the roots of a polynomial is only as hard as finding the roots of the factors. Your first polynomial cannot be solved exactly even for the simple case b=1, k=1, so how can it be solved for arbitrary b and k?

## exp(...) not exp^(...)...

@wrestler04 Remember, that should be exp(-10*x), not exp^(-10*x). Let me know if that works for you.

## tend <= 12 or tend= 0..50 -- can't have ...

On the one hand, it seems that you want tend to go from 0 to 12; and on the other hand, it seems that you want it to go from 0 to 50. You can't do both at the same time! Obviously, you know that; so I have to ask you to describe more precisely what you are trying to achieve.

Side note: You need to set the value of alpha. That problem won't manifest until you fix the tend problem.

## Change the subs line...

@emma hassan Change the subs command from subs({...}, Points) to

subs(XY, op(SOL), BC, Points);

There should not be any curly braces {}, and the order is important: BC must come after op(SOL).

## Change the subs line...

@emma hassan Change the subs command from subs({...}, Points) to

subs(XY, op(SOL), BC, Points);

There should not be any curly braces {}, and the order is important: BC must come after op(SOL).

## Not a limit on Matrix size...

@marc005 This limit, if it exists at all, is definitely not a limitation on Matrix size; it is a limit on the size of a Matrix that can be displayed in the browser.

You can easily select chunks of a large Matrix for browsing. Say M is the Matrix,

M[r1..r2, c1..c2]

gives (rows r1 to r2) X (columns c1 to c2).

## Boundary conditions...

@emma hassan I think that the values of U[0,4], ..., U[3,4] need to be filled by the boundary conditions. I don't think that they are meant to be solved for. I don't know enough about this type of problem to help you more with that.

Regardless of that, once the boundary grid points have values assigned, the commands are still GenerateMatrix and LinearSolve.

## Boundary conditions...

@emma hassan I think that the values of U[0,4], ..., U[3,4] need to be filled by the boundary conditions. I don't think that they are meant to be solved for. I don't know enough about this type of problem to help you more with that.

Regardless of that, once the boundary grid points have values assigned, the commands are still GenerateMatrix and LinearSolve.

## Simpler version...

I had used "%0.5s" as the output format code, which specifes a minimum width of 0 and a maximum width of 5. This can be simplified to just "%s" because the strings being passed in already have a maximum length of 5. Since the format code does not depend of the block length, there's no need for the variable WFO. So the final command can become

sprintf(cat("%s", " %s" \$ words-1), sscanf(T, cat(WFI \$ words))[]);

Notice the space before the second %s. That's what puts the spaces between the blocks.

## Simpler version...

I had used "%0.5s" as the output format code, which specifes a minimum width of 0 and a maximum width of 5. This can be simplified to just "%s" because the strings being passed in already have a maximum length of 5. Since the format code does not depend of the block length, there's no need for the variable WFO. So the final command can become

sprintf(cat("%s", " %s" \$ words-1), sscanf(T, cat(WFI \$ words))[]);

Notice the space before the second %s. That's what puts the spaces between the blocks.

## Anomaly...

@acer My results agree with yours now. I don't know what happened that caused my earlier results. May I assume that your results otherwise agree with mine: that additionally causes an additional copy of the variable to be created?

## Anomaly...

@acer My results agree with yours now. I don't know what happened that caused my earlier results. May I assume that your results otherwise agree with mine: that additionally causes an additional copy of the variable to be created?

## Version 17.00...

@acer Version 17.00. Do you get different results in another version?

## Version 17.00...

@acer Version 17.00. Do you get different results in another version?

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