readChannelID = 123456; 
WeightFieldID = 1; 
readAPIKey = 'ABCDE'; 

[Weight_Day1, timeStamps_Day1] = thingSpeakRead(readChannelID,'Fields',WeightFieldID,'dateRange',[datetime('today'),datetime('today')+days(1)],'ReadKey',readAPIKey);
[Weight_Day2, timeStamps_Day2] = thingSpeakRead(readChannelID,'Fields',WeightFieldID,'dateRange',[datetime('today')-days(1),datetime('today')],'ReadKey',readAPIKey);
[Weight_Day3, timeStamps_Day3] = thingSpeakRead(readChannelID,'Fields',WeightFieldID,'dateRange',[datetime('today')-days(2),datetime('today')-days(1)],'ReadKey',readAPIKey);

plot(timeStamps_Day1,Weight_Day1,timeStamps_Day2 + days(1),Weight_Day2,timeStamps_Day3 + days(2),Weight_Day3,'LineWidth', 2)

xlabel('Datum');
ylabel('Gewicht [kg]');
title('Gewicht der letzten 3 Tage');
legend({'heute','gestern','vorgestern'},'Location', 'best');
grid on