Using plot with dates stored in a cell array

Question

Askic V 2022-5-6

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https://ww2.mathworks.cn/matlabcentral/answers/1713100-using-plot-with-dates-stored-in-a-cell-array

评论： Askic V 2022-5-6

采纳的回答： Star Strider

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Hello Matlab experts,

I need your help plotting a price of some item on different days.

I have a cell array called dates with dates stored as strings (actually char) in the follwoing format: '1/22/20'

I also have an array of double with prices called prices. Lengths of these two arrays are of course identical. Now, I would like to plot the prices on different dates (as bars). If I use datetime, the date is converted to the year 0020. So,how to use plot function to plot dates on x axis and prices on y axis? Thank you very much.

>> class (dates{1})
ans =
char
>> datetime(dates{1})
ans = 
   22-Jan-0020
>> dates{1}
ans =
1/22/20

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Answer 1

Star Strider 2022-5-6

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I get a different result —

i = 1;
dates{i} = '1/22/20';
dtv = datetime(dates{i}, 'InputFormat','MM/dd/yy')
dtv = datetime
   22-Jan-2020

That appears to be correct.

This should lalso work in recent versions of MATLAB. See Date and Time from String Array for details.

.

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Answer 2

Voss 2022-5-6

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Here's one way to add 2000 to the years

dates = {'1/22/20','1/23/20','1/24/20','1/25/20'};
new_dates = datetime(regexprep(dates,'\d+$','${sprintf(''%d'',str2double($0)+2000)}'))
new_dates = 1×4 datetime array
   22-Jan-2020   23-Jan-2020   24-Jan-2020   25-Jan-2020

Then you can use them in plot or bar or whatever.

prices = [100 101 98 94];

bar(new_dates,prices)

hold on

plot(new_dates,prices,'-ro','LineWidth',2)

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Answer 3

Askic V 2022-5-6

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Thank you, I didn't know how to call datetime function properly. 'InputFormat','MM/dd/yy' is the answer I was looking for.

dates =
  1×5 cell array
    {'1/21/20'}    {'1/22/20'}    {'1/23/20'}    {'1/24/20'}    {'1/25/20'}
    
>> datetime(dates)
ans = 
  1×5 datetime array
   21-Jan-0020   22-Jan-0020   23-Jan-0020   24-Jan-0020   25-Jan-0020
>> dtv = datetime(dates, 'InputFormat','MM/dd/yy')
dtv = 
  1×5 datetime array
   21-Jan-2020   22-Jan-2020   23-Jan-2020   24-Jan-2020   25-Jan-2020