WHY CAN'T I PLOT THIS WITH "DATETIME"?
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Hello everyone,
I can't plot because of the error with "data time".
Does anyone know how I can solve this problem.
Thank you.
采纳的回答
Star Strider
2021-7-20
The first column is not a valid datetime array. It first needs to be converted to one.
Try this —
LD = load('LARSEN_MMEQ1.mat');
LARSENMMEQ1 = LD.LARSENMMEQ1;
LARSENMMEQ1.Var1 = datetime(LARSENMMEQ1.Var1, 'InputFormat','MM/dd/yyyy');
x = LARSENMMEQ1.Var1;
y = LARSENMMEQ1.Var2;
figure
plot(x, y)
grid
producing —
.
8 个评论
Pul
2021-7-20
Thank you.
But why do I get a line if I try to do this multiplication?
NEW=LARSENMMEQ1.Var2*10*0.35;
Star Strider
2021-7-20
I have no idea. It works correctlly foir me —
LD = load('LARSEN_MMEQ1.mat');
LARSENMMEQ1 = LD.LARSENMMEQ1;
LARSENMMEQ1.Var1 = datetime(LARSENMMEQ1.Var1, 'InputFormat','MM/dd/yyyy');
x = LARSENMMEQ1.Var1;
y = LARSENMMEQ1.Var2*10*0.35;
figure
plot(x, y)
grid
So I guess the question is what exactrly are you plotting?
Note — In the plot you posted in your Comment the independent variable is obviously not the datetime variable, so it may be that you are plotting 'NEW' as a funciton of ‘Var2’ (or the reverse of that). They would be linearly related, with an intercept of 0 and a slope of 3.5 (or the inverse of that).
.
Pul
2021-7-20
Star Strider
2021-7-20
My pleasure!
Of course the previous datetime import and conversion will not work, because the format is entirely different!
Try this —
LD = load('PAOLA_MMEQ1.mat');
PAOLAMMEQ = LD.PAOLAMMEQ;
dv = regexp(PAOLAMMEQ.Var1, '\d*\-\w*\-\d*','match');
PAOLAMMEQ.Var1 = datetime([dv{:}], 'InputFormat',"dd-MMM-yyyy").';
x = PAOLAMMEQ.Var1;
y = PAOLAMMEQ.Var2;
figure
plot(x, y)
grid
If you want to interpolate the missing data, use the fillmissing function, since there are 3008 NaN values in ‘y’. There are some anomalous values in Sep and Oct 2016, so you will have to decide on how to deal with them, so filloutliers and related functions are worth considering as well.
.
Pul
2021-7-21
Star Strider
2021-7-21
My pleasure.
There are no missing ‘x’ (datetime) values, so changing the plot to:
ym = ismissing(y);
yf = fillmissing(y,'linear');
figure
hpm = plot(x(ym), yf(ym), '.r', 'MarkerSize',3);
hold on
hpd = plot(x, y, '.-b');
hold off
grid
legend([hpd,hpm],'Data','Missing', 'Location','best')
shows the ‘y’ data in blue and all 3008 missing NaN values in red —
The anomalous values are the descending ‘spike’ in Sep-Oct 2016.
.
Pul
2021-7-21
Star Strider
2021-7-21
As always, my pleasure!
.
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