Lecture 12 Program Improvement Jeff Henrikson jhenriksumd edu

Lecture 12 Program Improvement Jeff Henrikson (jhenriks@umd. edu) http: //www. atmos. umd. edu/~jeff/aosc 347/ 1

Import/Export ASCII File with Known Data Format: Import Export n csvread n csvwrite n dlmread n dlmwrite n textscan n textread n fscanf Cell Array {. . } – access cellplot – visualize celldisp – display File with Unknown Data Format: n uiimport Import Wizard 2 Copyright © 2015 University of Maryland. This material may not be reproduced or redistributed in whole or in part without written permission from Xin-Zhong Liang

Atmospheric Sounding Open Explorer & go to http: //weather. uwyo. edu n Navigate to Upper Air Observations Soundings n n From the menu select Region: North America Type of plot: Text List Year: 2012 Month: Jul From: 15/12 Z To: 15/12 Z n Find Sterling VA (IAD) on the map and click 3 Copyright © 2015 University of Maryland. This material may not be reproduced or redistributed in whole or in part without written permission from Xin-Zhong Liang

urlread Copy & Paste urlname here Type in the Command Window >> a = urlread ('http: //weather. uwyo. edu/cgi. . . M=72403') Do not forget the quotes 4 Copyright © 2015 University of Maryland. This material may not be reproduced or redistributed in whole or in part without written permission from Xin-Zhong Liang

urlreads all characters in the source file Source file contains data and formatting text We need only the data not the formatting text 5 Copyright © 2015 University of Maryland. This material may not be reproduced or redistributed in whole or in part without written permission from Xin-Zhong Liang

urlread a is an array of thousands of characters! We have to locate the actual data within a 6 Copyright © 2015 University of Maryland. This material may not be reproduced or redistributed in whole or in part without written permission from Xin-Zhong Liang

Locate Data Start & End Data are bound by delimiters Scroll down Search for delimiters: strfind, regexp, strtok, etc. 7 Copyright © 2015 University of Maryland. This material may not be reproduced or redistributed in whole or in part without written permission from Xin-Zhong Liang

String Find / Length Position=533 Position=610 Linefeed >>L 1 = ' 1010. 0 93 23. 2 22. 4 95 17. 21 205 2 295. 5 >>Id = length(L 1)+1; % length of 1 st data line >>Ib = strfind(a, L 1); % position of 1 st char >>Ie = Ib + Id-1; % position of last char =610 345. 1 298. 6'; =78 =533 8 Copyright © 2015 University of Maryland. This material may not be reproduced or redistributed in whole or in part without written permission from Xin-Zhong Liang

Get Data Structure Line 1 Line 2 Start 533 611 End 610 687 >> Je = strfind (a, '</PRE>'); % data bound >> Ix = Je(1)-1; % last data char = 9892 >> Ln = (Ix-Ib+1)/Id; % total num of data lines = 120 for l = 1: Ln i 1 = Ib+(l-1)*Id; i 2 = i 1+Id; disp (a(i 1: i 2)) end 9 Copyright © 2015 University of Maryland. This material may not be reproduced or redistributed in whole or in part without written permission from Xin-Zhong Liang

Convert String to Data We can read multiple lines and convert each line into a 1 -d array >> b = str 2 num ( a (i 1: i 2) ) We need to convert the whole table into a 2 -d array # of rows = num of data lines to read # of columns = num of data fields (=11) >> if length ( b ) < 11 indicate missing data => ignore the line Missing data 10 Copyright © 2015 University of Maryland. This material may not be reproduced or redistributed in whole or in part without written permission from Xin-Zhong Liang

Save this code into an M-File called L 12 E 1. m Final Code close; clear; clc a = urlread('http: //weather. uwyo. edu/cgi-bin/sounding…M=74560'); L 1 =' 1010. 0 93 23. 2 22. 4 95 17. 21 205 2 295. 5 345. 1 298. 6'; Id = length(L 1)+1; % length of 1 st data line Ib = strfind(a, L 1); % position of 1 st char Ie = Ib + Id-1; % position of last char Je = strfind (a, '</PRE>'); % data bound Ix = Je(1)-1; % last data char Ln = (Ix-Ib+1)/Id; % total no of data lines Fn = 11; % no of fields Rn = 0; % no of valid data records for l = 1: Ln i 1 = Ib+(l-1)*Id; i 2 = i 1+Id; b = str 2 num (a(i 1: i 2)); if (length(b)==Fn) % add the data if no missing Rn = Rn+1; z(Rn, : ) = b(: ); end disp([z(: , 1), z(: , Fn)]); % for visual validation plot( z(: , 3), z(: , 1) ); set(gca, 'ydir', 'rev'); title('Sounding at Sterling'); xlabel('Temperature (C)'); ylabel('Pressures (h. Pa)'); 11 Copyright © 2015 University of Maryland. This material may not be reproduced or redistributed in whole or in part without written permission from Xin-Zhong Liang