Problem "Invalid first data argument" when plot a figure

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Ha Le Thanh
Ha Le Thanh 2017-12-25
编辑： ANKUR KUMAR 2017-12-26
Dear Colleagues My name is Le Thanh Ha. I am quite new to Matlab. I write a code to draw a figure, but the problem came out like "Invalid first data argument" and I do not know to what is the problem and how to figure out it. Please give me some advice to overcome it. Any comment and suggestion is greatly appreciated. Best

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ANKUR KUMAR
ANKUR KUMAR 2017-12-25
hold on
x=(1:127);
col={'b','r','k','y'}
data={vxo_cycle*0.1,gdp_cycle*0.01,pi_cycle,hoursworked_cycle}
for ii=1:4
plot(x,data{ii},col{ii})
hold on
end
  2 个评论
Ha Le Thanh
Ha Le Thanh 2017-12-26
Thank you so much for your help Regarding your revised code, please let me know how to legend lines as I described in my code. I make some changes but it is weird when matlab legend them thank you so much Best
ANKUR KUMAR
ANKUR KUMAR 2017-12-26
编辑：ANKUR KUMAR 2017-12-26
for legends
Just type legends once the loop ends
For example
A={randi(25,1,121),randi(25,1,121),randi(25,1,121),randi(25,1,121)} %You can write only one time. As it changes after execution
x=(1:121);
col={'r','b','k','g'}
for i=1:4
plot(x,A{i},col{i})
hold on
end
legend('First Data','Second Data','ThirdData','Fourth Data')

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更多回答（1 个）

Walter Roberson
Walter Roberson 2017-12-26
ppp=plot(1:127,vxo_cycle*0.1,'b',1:127,gdp_cycle*0.01,'r',1:127,pi_cycle,'k','LineWidth',hoursworked_cycle,'y','LineWidth',1.5);
has 'LineWidth' and then a variable. The 'LineWidth' is a named option and once you have started named options you cannot have any more positional parameters. However after that you then have 'y' which is not one of the named options: it is a positional line style option. But if there did happen to be a named option beginning with 'y' it would have to be followed by a value, which in this case would have to be that second 'LineWidth'. Then after that you have 1.5 which is not a valid option name.
Probably the first LineWidth should have been a variable name.

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