How to concatenate an array?

I have an array that is receiving data from the cloud, and I'm loosing the initial data while the array continue receiving the data.

How can I concatenate the data to keep the initial data in the array while continue receiving new data?

Here's the code and the array as a reference.

while true
    
    dataTT = (read(MQTTSignal));
    str = dataTT.Data;
    
    str = strrep(str, '{', ''); % remove opening bracket
    str = strrep(str, '}', ''); % remove closing bracket
    str = split(str,",");
    current = str2double(str(:,1));
    speed = str2double(str(:,2));
    time = str2double(str(:,3));
    subplot(2,1,1);
    plot(time,current);
    ylim([0,150]);
    grid ON
    title("Current");
    subplot(2,1,2);
    plot(time,speed);
    ylim([0,1000]);
    grid ON
    title("Speed");
    drawnow
    pause(3)
end

Answer 1

[Matt J]

dataTT=[];
while true
    
    dataTT = [dataTT,  read(MQTTSignal)];
    str = dataTT(end).Data;
    
    ...

end

[Luis Ricardo Rivera Goitia]

It got me an error msg

Error using ()

Subscripting into a table using one subscript (as in t(i)) is not supported. Specify a row subscript and a variable

subscript, as in t(rows,vars). To select variables, use t(:,i) or for one variable t.(i). To select rows, use t(i,:).

Error in MQTT_ESP32_Current_Speed_Graphs_2nd_Trial (line 21)

str = dataTT(end).Data;

[Matt J]

Apparently your dataTT is not in struct form.

dataTT = [dataTT,  table2struct( read(MQTTSignal)  )];

[Luis Ricardo Rivera Goitia]

Using table2struct function gave me also an error and has changed the str array to only three rows of data (separated)

Index in position 2 exceeds array bounds. Index must not exceed 1.

Error in MQTT_ESP32_Current_Speed_Graphs_2nd_Trial (line 30)

speed = str2double(str(:,2));

I changed the code to the following and I got the graphs for a moment until the program fails giving me this error.

Error using tabular/horzcat

All tables being horizontally concatenated must have the same number of rows.

Error in MQTT_ESP32_Current_Speed_Graphs_2nd_Trial (line 20)

dataTT = [dataTT,(read(MQTTSignal))];

dataTT=[];

while true

dataTT = [dataTT,(read(MQTTSignal))];

%dataTT = [dataTT, table2struct( read(MQTTSignal) )];

str = dataTT.Data;

str = strrep(str, '{', ''); % remove opening bracket

str = strrep(str, '}', ''); % remove closing bracket

str = split(str,",");

current = str2double(str(:,1));

speed = str2double(str(:,2));

time = str2double(str(:,3));

[Matt J]

dataTT = [dataTT,  table2struct( read(MQTTSignal,"ToScalar",1)  )];

[Luis Ricardo Rivera Goitia]

It gave me this error that is not recognized

Error using MQTT_para_Appdesigner

'ToScalar' is not a recognized parameter. For a list of valid name-value pair arguments, see the documentation for this function.

[Matt J]

dataTT = [dataTT,  table2struct( read(MQTTSignal)    ,"ToScalar",1  )];

[Luis Ricardo Rivera Goitia]

Apparently it worked, the only thing is that dataTT is now divided in two, and one of this two is cumulating the data in segments, I think that would help me to avoid loosing the previous information, thx.

Here's an image about its behavior:

As you can see Data column is storing the dataTT received from MQTT in segments.