create a matrix in a function

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Tony Montgomery 2014-9-6

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评论： Star Strider 2014-9-6

I have to create a function called ssolve. in the function i need to create an array that can accept 3 variables a, b, n. these variables need to be placed in a matrix. example a needs to be in row 1 column 2, and b needs to be in row 20 columns 1-19. ones must be diagonal, and the rest are zero. in another array, (1by20) i need to have the first 16 to be 1-16, the 17th must be n-2, 18th must be 0, and the last must be n. how can I put that in, ive tried

c=ones(1,20);
m=diag(c);
m(1,2)=a;
m(20,:)=[b(1,19) 1];

but i get an error, what am i doing wrong?

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Answer 1

Star Strider 2014-9-6

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You’re close!

Change the m(20,:) assignment to:

m(20,:)=[b*ones(1,19) 1];

MATLAB creates automatically incremented vectors using the colon ‘:’ operator. To create a vector that goes from 1 to 7:

v = 1:7;

If you wanted to change the 5th element of v here to 100:

v(5) = 100;

Display v to see the result by just typing v in the Command Window.

That is not the exact answer to the second part of your question, but it will get you started.

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Tony Montgomery 2014-9-6

THANK YOU THANK YOU THANK YOU. You really are like my best friend right now. I'm sorry to keep asking questions but I'm new at this and not very good at it so thank you so much again!!