How to apply a equation to specific rows in a matrix

If I have a matrix m like:

m=[0   340.216815000000
1.56250000000000    570.718050000000
4.68750000000000    769.256473000000
7.81250000000000    1176.42951000000
10.9375000000000    1632.88855600000
18.4375000000000    2099.99990500000
25.9375000000000    2099.99990500000
33.4375000000000    2099.99990500000
40.9375000000000    2099.99990500000
48.4375000000000    2099.99990500000
0   331.115127000000
1.53698699999995    510.419428000000
4.61084000000005    719.346166000000
7.68469200000004    1145.58672900000
10.7585449999999    1583.81915100000
18.1358640000001    2099.99990500000
25.5130620000000    2099.99990500000
32.8903809999999    2099.99990500000
40.2675780000000    2099.99990500000
47.6448969999999    2099.99990500000];

and a matrix n like:

n=[0	159.846351000000
1.52099599999997	343.757153000000
4.56286599999999	412.372440000000
7.60473600000000	926.872313000000
10.6466060000000	1063.47274800000
17.9471440000000	1079.82945400000
25.2475589999999	1200.00004800000
32.5480960000000	1200.00004800000
39.8486330000001	1200.00004800000
47.1491699999999	1200.00004800000
0	186.247796000000
1.49536100000000	386.090606000000
4.48608399999989	477.258742000000
7.47680700000001	775.100648000000
10.4676509999999	1004.91941000000
17.6453859999999	1075.44088400000
24.8232419999999	1200.00004800000
32.0009769999999	1200.00004800000
39.1787110000000	1200.00004800000
46.3565670000000	1200.00004800000];

how to build a vector E which matches that when m(:,1) is lower than 10, then use this formula:

1. (m(:,2).^2).*(3*(n(:,2).^2));

and when 10 < m(:,1) <= 25, use:

2. (m(:,2).*2)

the results would be this:

E = [8872341649.18581
115469679048.928
301885906398.286
3566916094097.57
3265.77711200000
4199.99981000000
4199.99981000000
4199.99981000000
4199.99981000000
4199.99981000000
662.230254000000
1020.83885600000
1438.69233200000
2291.17345800000
3167.63830200000
4199.99981000000
4199.99981000000
4199.99981000000
4199.99981000000
4199.99981000000];

[Stephen23]

Your example output does not match your description: rows 7, 8, 9, 10, 17, 18, 19, and 20 of m do not match either of the conditions that you describe, and yet you show data in those rows of the output matrix. Please explain how that data should be generated.

Answer 1

[Stephen23]

X = m(:,1)<=10;
Y = 10<m(:,1) & m(:,1)<=25;
Z = nan(size(m,1),1);
Z(X) = m(X,2).^2 .* 3.*n(X,2).^2;
Z(Y) = m(Y,2).*2;

Giving:

>> Z
Z =
  8872341649.185812
  115469679048.9282
  301885906398.2859
  3566916094097.571
  3265.777112
  4199.99981
  NaN
  NaN
  NaN
  NaN
  11409367861.74257
  116507562823.7022
  353594015029.8446
  2365339054254.324
  3167.638302
  4199.99981
  NaN
  NaN
  NaN
  NaN

[Philippe Corner]

thanks for ypur answer stephen, why it is not repeating 4199.99981 values in rows 7-10 and 17-20?

[Stephen23]

"why it is not repeating 4199.99981 values in rows 7-10 and 17-20?"

Simply because nowhere in your question did you state that as a requirement, or explain anything about how to fill in "missing" values: do you want to repeat the last numeric value until the next condition is fulfilled? What happens at the start of the ouput vector if the first row/s of m do not fulfill either of those conditions?

[Philippe Corner]

Sorry you are right, they should be filled with (m(:,2).*2)

[Stephen23]

X = m(:,1)<=10;
Z = m(:,2).*2;
Z(X) = m(X,2).^2 .* 3.*n(X,2).^2;

Giving:

>> Z
Z =
  8872341649.185812
  115469679048.9282
  301885906398.2859
  3566916094097.571
  3265.777112
  4199.99981
  4199.99981
  4199.99981
  4199.99981
  4199.99981
  11409367861.74257
  116507562823.7022
  353594015029.8446
  2365339054254.324
  3167.638302
  4199.99981
  4199.99981
  4199.99981
  4199.99981
  4199.99981