Dear all

I have data and a vector d. 
I would like to sum the elements of the vector d corresponding to the index  of the element data <=0.01 

Step 1: we select the index of data that corresponds to data<=0.01

step 2: we select the consecutive index corresponding to data<=0.01

Step 3 : we sum the element of d corresponding to the previous index

step 4: update d=d/number(index) ;

Please see my attached code. It's done by hand how can reformulate the code.

code_vector.mw

many thanks

Dear all

I applied the definition of a permutation matrix to a given matrix A to obtain a Tridiagonal Toeplitz matrix, but I haven't any idea why the final result looks strange.

Permutation_matrix.mw

Many thanks

Dear all

Using maple I can't obtain an exact solution, my goal for which initial condition can the solution diverge to infinity if maple can not give us a solution.

special_condition_diverge.mw

many thanks

Dear all

I would like to compute a Laurent of a given function at an isolated point.

laurent_series.mw

thanks for your help

Dear all

I would like to solve a linear system A X=b whee A is a matrix n times n

If A is a tri-diagonal matrix, how can we write simple code to make A upper-triangular and then we solve the system using backward substitution

many thanks