# How to create matrices from a table and extract specific data from it to make plots?

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James on 29 Dec 2020
Commented: Stephen on 29 Dec 2020
I'm sorry if the title is confusing. But I'm stuck at a point and I will appreciate any tip or help!
I'm reading a series of AIS data from an excel file (.xlsx) and one of my targets is to plot the trajectories of each vessel. But I also need to preserve/store all data for further analysis.
I've attached a sample data file. (sample.xlsx) I have the following code. (My apologies for the sloppiness, any tips for improvements is appreciated)
% Load the AIS data file from the path specified
% Adjust the numbers according to the columns (mmsi, time, LAT, LON, SOG, COG, L and B))
AISdata = Data_file(:, [2, 3, 4, 6, 7, 8, 9, 10]);
% Sorting the data. First by MMSI and then by Time
AISdata_srt = sortrows(AISdata, [1 4]); % [MMSI TIME]
% Ship dimension table
dim = AISdata_srt(:, [1, 7, 8]);
dimensions = unique(dim(:,:), 'rows');
% Grouping the data series by MMSI
G = findgroups(AISdata(:,1));
M = accumarray(G, (1:size(AISdata,1)).', [], @(x){AISdata(x,:)});
What I think I need is a loop to take each cell "group" from M and convert it to an array. Then extract its Latitude-Longitude data as X-Y (cartesian) data and plot them. All I could think of is a pseudo loop like this. But I don't know how to implement it.
for 1:(Number of Groups in M)
> (Take one group)
> (convert it to a matrix)
> (Extract LON LAT data)
> (plot hold on)
end
How can I do this?
Again, my apologies for the sloppy code, I'm still learning.
Stephen on 29 Dec 2020

Cris LaPierre on 29 Dec 2020
As Adam told you in your previous post, you can just work with the data in the table. No need to extract it somewhere else. See the page Access Data in Tables.
% Load the AIS data file from the path specified
% Grouping the data series by MMSI
G = findgroups(AISdata.mmsi);
figure
hold on
for g = 1:max(G)
plot(AISdata.lat(G==g),AISdata.lon(G==g),'LineWidth',2)
end
hold off
legend('Location','northwest')
James on 29 Dec 2020
This is great! Thanks, Cris!