if number is already recorded don't record

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C.G.
C.G. on 22 Jan 2021
Edited: C.G. on 25 Jan 2021
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)')

Answers (1)

Superficial
Superficial on 22 Jan 2021
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.
  1 Comment
C.G.
C.G. on 25 Jan 2021
Edited: C.G. on 25 Jan 2021
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

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