if number is already recorded don't record

My code reads data from multiple csv files, and identifies how many balls move past a certain y coordinate in each time step and stores this in a new variable 'grains'.

This is currently cumulative, so any ball with y coordinates <-0.13 is recorded in each time step even if they were recorded previously.

I want to adapt this code, to only record if the ball coordinates are <-0.13 and the particle ID hasnt already been recorded in a previous time step. I know I need to add something to the if loop but I am unsure how to write this.

Could anybody provide me with a way to do this?

%% input 
%input data from each .csv file into matlab 
%need particle id, velocity and coordinates stored

files = dir('*.csv'); %dir list                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       s the files in a folder. In the specified folder, recognise all the .csv files
num_files = length(files); %specify how many files have been found and call it num_files
particledata = cell(length(files), 1); %create a cell array the same length as the number of files in one column
%for all the files found in the specified folder, read the tables of data and fill the empty cell array 'results' with the data in each .csv file
for a = 1:num_files
  particledata{a} = readtable(files(a).name);
end 

%% particles leaving the rice pile
%for each .csv file (cell in the array), calculate the number of particles
%after a between certain y coordinates
ymax = -0.13;
for b = 1:length(particledata)
    %save all the rows in the 6th column (y-coordinates) of each cell as a new variable y
    y{b} = particledata{b}(:,6);
    %save all the rows in the 1st column (particle ID) of each cell as a new variable id
    id{b} = particledata{b} (:,1);
    %use the function table2array to turn the format of the data from a table to an array
    y_array{b} = table2array(y{b});
    %for all the rows in the array, if the x coordinate goes beyond the outlet
    %of the rice pile, display 'grain left rice pile'
    if  y_array{b}<ymax
        disp('grain left rice pile');
    end
    %sum the total number of grains leaving the rice pile in each cell, and save into a new variable 'grains'
    grains{b} = sum(y_array{b}<ymax);
    fprintf('A total of %d grains left the rice pile\n',grains{b});
end 

%% plots for just 1 power spectra for 1 experiment
%number of csv files = number of time steps the model is run for (seconds)
totalruntime = num_files;
time = 1:totalruntime;
%convert the cell file to a double file to allow plotting of data
grains = cell2mat(grains);

%mass efflux vs. time
%plot 'grains left rice pile' vs. time step as a bar graph
%0.01 sets the width of each bar
figure(1)
bar(time,grains, 0.01, 'EdgeColor', 'r')
title('mass efflux')
xlabel('Time (S)')
ylabel('Mass Efflux (No. of Particles)')

Answer 1

[Superficial]

If I've not misread the situation, it's just a simple subtraction isn't it?

newgrains at timestep10= total number of grains at timestep10 - total number of grains at timestep9

newgrains=zeros(1, length(grains));
for i=2:length(grains)
    newgrains(i)=grains(i)-grains(i-1)
end

You could probably put that inside your 'for' loop if you wanted, but it should work OK (just a bit slower) at the end of your code.

Alternatively, you can look at using the histogram instead of bar plot.

[C.G.]

I have given each particle an ID number.

I want the script to 1. identify when the grain coordinates are <-0.13, and 2. only store this number in 'grains' if the particle Id is not already recorded.

ymax = -0.13;
for b = 1:length(particledata)
    %save all the rows in the 1st and 6th column (ID and y-coordinates) of each cell as a new variable y
    y{b} = particledata{b}(:,[1 6]);
    %use the function table2array to turn the format of the data from a table to an array
    y_array{b} = table2array(y{b});
    %for all the rows in the array, if the x coordinate goes beyond the outlet
    %of the rice pile, display 'grain left rice pile'
    if  y_array{b}(:,2)<ymax
        disp('grain left rice pile');
    end
    %sum the total number of grains leaving the rice pile in each cell, and save into a new variable 'grains'
    grains{b} = sum(y_array{b}(:,2)<ymax);
    fprintf('A total of %d grains left the rice pile\n',grains{b});
end