Reduced row echelon form: Difference between revisions

=={{header|FreeBASIC}}==

Include the code from [[Matrix multiplication#FreeBASIC]] because this function uses the matrix type defined there and I don't want to reproduce it all here.

<lang freebasic>#include once "matmult.bas"

sub rowswap( byval M as Matrix, i as uinteger, j as uinteger )

dim as integer k

for k = 0 to ubound(M.m, 2)

swap M.m(j, k), M.m(i, k)

next k

end sub

function rowech(byval M as Matrix) as Matrix

dim as uinteger lead = 0, rowCount = 1+ubound(M.m, 1), colCount = 1+ubound(M.m, 2)

dim as uinteger r, i, j

dim as double K

for r = 0 to rowCount-1

if lead >= colCount then exit for

i = r

while M.m(i, lead) = 0

i += 1

if i = rowCount then

i = r

lead += 1

if lead = colCount then exit for

endif

wend

rowswap M, r, i

K = M.m(r,lead)

if K <> 0 then

for j = 0 to colCount-1

M.m(r,j) /= K

next j

endif

for i = 0 to rowCount-1

if i <> r then

K = M.m(i, lead)

for j = 0 to colCount-1

M.m(i,j) -= M.m(r,j) * K

next j

endif

next i

lead += 1

next r

return M

end function

dim as Matrix M = Matrix (3, 4)

dim as Matrix N

M.m(0,0) = 1 : M.m(0,1) = 2 : M.m(0,2) = -1 : M.M(0,3) = -4

M.m(1,0) = 2 : M.m(1,1) = 3 : M.m(1,2) = -1 : M.m(1,3) = -11

M.m(2,0) = -2: M.m(2,1) = 0 : M.m(2,2) = -3 : M.m(2,3) = 22

dim as integer i, j

N = rowech(M)

for i=0 to 2

for j = 0 to 3

print N.m(i, j),

next j

print

next i</lang>

{{out}}

<pre>

1 0 0 -8

-0 1 0 1

-0 -0 1 -2

</pre>