Calculation of a column

Hi,

I have a column with 53 rows of different numbers. I only want to do formula calculation until the 45th row and the remaining 8 rows I want to make them the same value. All the results will be compile in the same column. May I know how that can be done?

With Altitude having the column (53 rows of number),

To = 288.15; % Temperature in ISA [K]

for i = 1:53

Ta (i) = To-0.0065*Altitude(i); % Temperature at altitude [K]

end

From above code, how do I make the calculation stop at 45th row and the remaining 8 rows will have the value of 216.65? and all new 53 rows of values will be under 1 column?

Thank you very much.

Answer 1

[Voss]

To = 288.15; % Temperature in ISA [K]

% pre-allocate Ta to be the same size as Altitude (53x1), with all elements 216.65
Ta = 216.65*ones(size(Altitude));

% calculate the first 45 elements of Ta:
Ta(1:45) = To-0.0065*Altitude(1:45); % Temperature at altitude [K]

[Ke Yeun Yong]

Thank you vey much.

May I know how do I convert the row results into column results for my for-loop as follow?

Po = 101325; % Pressure in ISA [Pa]

for i = 1:53

Pa(i) = Po*(1-2.2558E-5*Altitude(i))^5.25864; % Pressure in altitude [Pa]

end

The result will be shown as 1X53 but I want to change it to 53X1

[Voss]

Pre-allocate Pa as a column vector, like this:

Pa = zeros(53,1);

Although if you avoid the for loop and do the calculation for all elements at once, like this:

Po = 101325; % Pressure in ISA [Pa]
Pa = Po*(1-2.2558E-5*Altitude).^5.25864; % Pressure in altitude [Pa]

Then you don't have to pre-allocate, and Pa will be the same size as Altitude.

In case Altitude is a row vector or an array with some other orientation, you can use it as a column vector by using (:) in the calculation, which makes Pa a column vector:

Po = 101325; % Pressure in ISA [Pa]
Pa = Po*(1-2.2558E-5*Altitude(:)).^5.25864; % Pressure in altitude [Pa]

[Ke Yeun Yong]

Hi,

CDO = 0.023; % Zero-lift drag coefficient

K = 0.044; % Lift-induced drag factor

MTOW = 79010; % Maximum take-off mass [kg]

W = MTOW*9.81; % Weight in N

A= Thrust_22K/W;

B = sqrt((A.^2)+(12*CDO*K));

Cl = (6*CDO)/(A+B)

Thrust_22K is a column with 53 rows and I am trying to calculate for Cl as above but the results on shows the first row result and the rest is zero. May I know what have i did wrong?

Thank you very much.

[Voss]

Use ./ for element-wise division.

Cl = (6*CDO)./(A+B);

See the tables of operators here: https://www.mathworks.com/help/matlab/matlab_prog/array-vs-matrix-operations.html