for loop with calculations across rows

Hi there,

I have used MATLAB for less than a year and I now think I need to get the FOR loop (no previous experience).

a = [1 2 3 4 5 6; 1.05 1.08 0.98 1.0 1.01 0.93]'

a =

1.0000 1.0500

2.0000 1.0800

3.0000 0.9800

4.0000 1.0000

5.0000 1.0100

6.0000 0.9300

Need a FOR loop in MATLAB to calculate the EOD vector below

Calculation in Excel

C2 is A1*B1

C3 is C2*B3 + A2*B3

Etc.

I intend to use this on tables with more than 100,000 lines, but will implement on subgroups (assumption is to use splitapply). I think it could be sensible to consider preallocate to a vector with zeros, great if the solution can include preallocation and if you have considerations on how the FOR loop can be integrated into splitapply.

Thank you for your help, kind regards,

William

[William Ambrose]

Sorry I see that an error has made its way into the description. Should be

Calculation in Excel

C2 is A1*B1

C3 is C2*B3 + A3*B3

Etc.

Answer 1

[William Ambrose]

Found out :

a = [1 2 3 4 5 6; 1.05 1.08 0.98 1.0 1.01 0.93]' ;

x = zeros(length(a),1) ;

x(1) = a(1,1).* a(1,2) ;

for n = 2:length(a)

x(n) = a(n,1) * a(n,2) + x(n-1)*a(n,2);

end

b = [a,x]

b =

1.0000 1.0500 1.0500

2.0000 1.0800 3.2940

3.0000 0.9800 6.1681

4.0000 1.0000 10.1681

5.0000 1.0100 15.3198

6.0000 0.9300 19.8274

>>