Creating a loop that performs actions for each set of values linked to a unique (but random) ID

I have a csv file containing CTD data with columns for: Cast ID (cast); latitude; longitude; depth; salinity; temperature. The objective is to create sound speed profiles for each unique cast. Each cast has a varying number of records attached to it (i.e. a cast may have measurements at 15 different depths, and the next may have 7 measurements). I would like to create a loop for this, but I'm having trouble with:

1. How to pass the loop from the first cast to the second etc - the cast IDs are effectively random, i.e. they do not change with any pattern.
2. How to ensure that the only data being used in each sound speed calculation is only associated with that individual cast.

Verbiosly, the script would be along the lines of:

for each unique cast ID

run sound speed profile equation

output plot

end

With the loop repeating for each cast ID.

Is anyone able to point me in the direction of how to format the loop so it runs for each unique but random ID, and how to ensure that each sound speed profile is only calculated based on records associated with that unique ID? Thanks!

[Mathieu NOE]

hello

have you already written the code ? are you willing to share it ?

also if you can share a csv input data file, that would help

[Aryn Sanojca]

Hi Mathieu, thanks for the response. I don't actually have any code written as I'm not sure where to start. The sound speed equation is just called from something prewritten. I've attached the input data file.

Answer 1

[Alan Stevens]

Does this help:

%% Setup the Import Options and import the data
opts = delimitedTextImportOptions("NumVariables", 9);

% Specify range and delimiter
opts.DataLines = [1, Inf];
opts.Delimiter = ",";

% Specify column names and types
opts.VariableNames = ["cast1", "Var2", "Var3", "Var4", "Var5", "Var6", "depth", "temp", "sal"];
opts.SelectedVariableNames = ["cast1", "depth", "temp", "sal"];
opts.VariableTypes = ["double", "string", "string", "string", "string", "string", "double", "double", "double"];

% Specify file level properties
opts.ExtraColumnsRule = "ignore";
opts.EmptyLineRule = "read";

% Specify variable properties
opts = setvaropts(opts, ["Var2", "Var3", "Var4", "Var5", "Var6"], "WhitespaceRule", "preserve");
opts = setvaropts(opts, ["Var2", "Var3", "Var4", "Var5", "Var6"], "EmptyFieldRule", "auto");

% Import the data
tbl = readtable("CTD_Cleaned.csv", opts);

%% Convert to output type
cast1 = tbl.cast1;
depth = tbl.depth;
temp = tbl.temp;
sal = tbl.sal;

%% Clear temporary variables
clear opts tbl

%  All the above comes from MATLAB's Import Data wizard 

%% Find unique IDs by looking for zero depths
ix = find(depth==0);
ID = cast1(ix);

%% Find corresponding depths, temperatures and salinities

for i = 1:numel(ix)-1
    p1 = ix(i); p2 = ix(i+1)-1;
    dpth = depth(p1:p2);
    T    = temp(p1:p2);
    saln = sal(p1:p2);
  
    % Now put your sound speed profile calculation here for ID(i)
    
end