Symbiological output using 'syms' and 'pretty' commands

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Jay 2021-11-25

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1595449-symbiological-output-using-syms-and-pretty-commands

评论： Star Strider 2021-11-29

采纳的回答： Star Strider

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Hi all,

I am having issues outputting the factored polynomial using the below commands using MatLab 2021b (academic license) sybologically.

I have the Symbology Toolbox 'Installed' and can't determine what the issues is.

The online R2021b 'Run' command outputs (MatLab Desired Output.GIF red box) also aren't outputting in my Command Window on my license.

The 'Attachment with run function' also isn't working for the 2021b forum posting. When

I= imread('PolySolver.GIF')
Error using imread>get_full_filename (line 569)
File "PolySolver.GIF" does not exist.

Error in imread (line 371)
    fullname = get_full_filename(filename);

is ommited (online) the answer (ans) is outputted as desired (MatLab Desired Output.GIF).

%% Factor Command 
syms x
f1 = factor (x^3 + 2*x -3, x) % Directly below not showing on PC version of 2021b 
% Make the factorisation 'pretty'
% Status: Not working
pretty(f1)
% Output
I= imread('PolySolver.GIF')
imshow = I % Attachment with run function not working for 2021b - Online posting

% Desired
(x - 1), (x^2 + x + 3)

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Star Strider 2021-11-25

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https://ww2.mathworks.cn/matlabcentral/answers/1595449-symbiological-output-using-syms-and-pretty-commands#answer_840024

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Experiment with the indexing into the expressions (since this is a straightforward solution to a number of otherwise difficult problems in MATLAB).

Are these the desired results?

%% Factor Command

syms x

f1 = factor (x^3 + 2*x -3, x) % Directly below not showing on PC version of 2021b

f1 =

f1(1)

ans =

f1(2)

ans =

% Make the factorisation 'pretty'

% Status: Not working

pretty(f1)

( 2 ) x - 1, x + x + 3

% Output

I= imread('https://www.mathworks.com/matlabcentral/answers/uploaded_files/812799/PolySolver.GIF');

imshow(I) % Attachment with run function not working for 2021b - Online posting

Right-click to copy the full file name to open the file in the in the online Run application. (This works except for .m files, that are painful to use with it.)

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Star Strider 2021-11-29

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As Walter described, creating dynamic veriable names is rarely a good idea. (One generally supported use is to assign a matrix row or column to a single variable if it will be used a lot later in the code. This is just more convenient. However if dynamic variables are to be used in a loop or some such, they become very unwieldy very quickly, and create slow, inefficient code.) Note that I simply referred to ‘f1’ as matrix elements ‘f1(1)’ and ‘f1(2)’.

the relativelly new string variable type has some advantages that character and symbolic variables and arrays do not —

syms x

f1 = factor (x^3 + 2*x -3, x) % Directly below not showing on PC version of 2021b

f1 =

f1s = string(f1)

f1s = 1×2 string array

"x - 1" "x + x^2 + 3"

f1s_plus = f1s(1) + " " + f1s(2)

f1s_plus = "x - 1 x + x^2 + 3"

‘have I confused you as to my desired output and way of thinking?’

To an extent, yes. Remember the Stones song ‘You Can’t Always Get What You Want’? That applies here. Some things are possible, and some just aren’t. Experiment with the string variable properties, since they likely come closest to what I believe is the desired result (although I’m still not certain what that is).

Jay 2021-11-29

Thanks @Star Strider, I'll look into the new string variable and if it doesn't do as I would like, I'll just have to get used to the output and deal with it :).

Thanks again for your help gents.