How to replace char 'null' in number 0?

Question

Bizzy Dy 2018-8-9

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/414208-how-to-replace-char-null-in-number-0

评论： Guillaume 2018-8-9

Hi! I`ve got a problem with using plot function cause there is some 'null's (char type) in my data files . So i would like to change/replace that nulls in 0 (num) . Could someone help to find useful function or to offer other solution.

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Bizzy Dy 2018-8-9

编辑：Bizzy Dy 2018-8-9

在 MATLAB Online 中打开

%%read
clear all, close all;
h=tdfread('result_3259_m.tsv','tab')
%%get
time=getfield(h,'time')
Qus=getfield(h,'input0x2Eflowrate0x2Eflowmeter')
P1=getfield(h,'input0x2Epressure0x2Ebefore')
P2=getfield(h,'input0x2Epressure0x2Eafter')
P3=getfield(h,'input0x2Epressure0x2EforFlowmeter')
T1=getfield(h,'input0x2Etemperature0x2Ebefore')
T2=getfield(h,'input0x2Etemperature0x2Eafter')
A=getfield(h,'input0x2Evalve0x2Eposition')
% bezm=getfield(h,'BEZM')
% rmse=getfield(h,'RMSE')
%%dateformat
formatIn='yyyy-mm-ddTHH:MM:ssZ'
% ds=datetime(time,'InputFormat','yyyy-mm-ddTHH:MM:ssZ')
    dn=datenum(time,formatIn)
%%draw
dateborder1=datenum(2018,07,01,0,0,0)
dateborder2=datenum(2018,07,26,0,0,0)
subplot(2,1,1);
    plot(dn,P1,'y');hold on;
    plot(dn,P2,'c');hold on;
    plot(dn,P3);hold on;
    plot(dn,T1,'m');hold on;
    plot(dn,T2,'g');hold on;
    plot(dn,A,'r');hold on;
datetick('x','dd.mm, HH:MM','keepticks')
datetickzoom
    axis([dateborder1, dateborder2, -20 , 100])
        legend('P1','P2','P3','T1','T2','A')
            grid on
%             grid minor
subplot(2,1,2);
%     plot(dn,bezm);hold on;
    plot(dn,Qus,'r');hold on;
%   plot(dn,rmse,'g');hold on;
datetick('x','dd.mm, HH:MM','keepticks')
datetickzoom('x',1)
% xticks(0:10:100)
     axis([dateborder1, dateborder2, 0 , max(Qus)])
%          legend('Bezm','Qus')
            grid on
%             grid minor

Bizzy Dy 2018-8-9

done

Guillaume 2018-8-9

Please do not close questions that have been answered.

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Answer 1

Guillaume 2018-8-9

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/414208-how-to-replace-char-null-in-number-0#answer_332159

编辑：Guillaume 2018-8-9

在 MATLAB Online 中打开

It's much easier to read your file with readtable (which also does not require any toolbox). It is trivial with readtable to convert the 'null' to 0 and read everything else as number.

t = readtable('result_3259_m.tsv', 'FileType', 'text', 'TreatAsEmpty', 'null', 'EmptyValue', 0);
t.time = datetime(t.time, 'InputFormat', 'yyyy-MM-dd''T''HH:mm:ss''Z''');

For further processing you may even want to convert the table to a timetable

I would also recommend that you do not extract the table columns into variables with meaningless names. Just use the table variables directly:

plot(t.time, t.input_flowrate_bezm, 'DatetimeTickFormat', 'dd.MM, HH:mm');

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Bizzy Dy 2018-8-9

Thank you so much!

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Answer 2

Ameer Hamza 2018-8-9

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/414208-how-to-replace-char-null-in-number-0#answer_332139

The image shows a struct which char arrays as fields. You can use strrep() to replace the elements of a char array. Although it will still not work with the plot() function because the elements are char arrays, not numeric values. You might need to use str2num() to convert char values t numeric before using plot().