Create a single for loop for multiple conditions

Hi, I have a for loop with several calculations. There are three conditions for which the calculations are more or less the same. How can I formulate the code so that I have just one for loop for multiple conditions ? Ex. A same set of speed calculations for a boat a) Moving in still water b) Moving with the current c) Moving against the current

[Birdman]

Why don't you share the code? How can we help you without seeing the code?

[DIP]

 1. Still River
Boat_Speed=40;
for i=1:41
    % Vehicle speed
    VMPG(i) = Vehicle_Speed; % mph
    Vmps(i) = Vehicle_Speed*0.44704; % m/s

    % Rolling resistance force (N)
    Fr = Croll*Vwt;

    % Frontal area (m2)
    Af = 0.84*Vht*Vwd;

    % Air density (kg/m3)
    rho = Pamb/R/Tamb; ... many more calculations

   2. Downstream
Boat_Speed=40;
for i=1:41
    % Vehicle speed
    VMPG(i) = Vehicle_Speed; % mph
    Vmps(i) = Vehicle_Speed*0.44704; % m/s

    % Rolling resistance force (N)
    Fr = Croll*Vwt;

    % Frontal area (m2)
    Af = 0.84*Vht*Vwd;

    % Air density (kg/m3)
    rho = Pamb/R/Tamb; ...  

3. Upstream
Boat_Speed=40;
for i=1:41
  % Vehicle speed
  VMPG(i) = Vehicle_Speed; % mph
  Vmps(i) = Vehicle_Speed*0.44704; % m/s

    % Rolling resistance force (N)
    Fr = Croll*Vwt;

    % Frontal area (m2)
    Af = 0.84*Vht*Vwd;

    % Air density (kg/m3)
    rho = Pamb/R/Tamb; ... many more calculations

[Birdman]

What is your condition in this cases?

[DIP]

there are three cases , the boat speed in still water, moving downstream and moving upstream. The for loop for each case is almost the same. Can I combine the three cases in a single for loop ?

[Moritz]

I have to say I don't see any difference between the different cases. Can you pin point it to me? Anyhow, why don't you use one for loop and a switch case within for the differences in calculations (alternatively an if else structure as there are only 3 different cases). Does this help?

[RobF]

I also have to say that your conditions (still river - downstream - upstream) don't seem to change anything concerning the for loop. Where the point where the condition gets relevant?

[DIP]

Moritz, RobF, the speeds are different, how can I input multiple conditions for speed and use only one for loop ?

[Walter Roberson]

"the speeds are different"

Not in the code you posted.

Answer 1

[A. Sawas]

I suggest you use switch statement like this:

Boat_Speed=40;
% set the following variable based on the current water conditions
water_condition = 'Still River';
for i=1:41
  % your code before calculating the speed
  % calculate vehicle speed at different water conditions
  switch water_condition
    case 'Still River'
      % your code to calculate speed in still river conditions
    case 'Downstream'
      % your code to calculate speed in downstream conditions
    case 'Upstream'
      % your code to calculate speed in upstream conditions
    otherwise
      warning('Unexpected water condition.');
  end
  % your code after calculating the speed
end