numpy.ndarray doesn't have count attribute

First convert it into a list, by using list() function. Then use the count method to count.

list(nda).count(1)

Convert a dataset to matrix

For the simplest case when the dataset only contains numbers, this double function can be used to convert a dataset to matrix, or a vector if there is only one variable in the dataset:

m=double(ds)

remove any rows that contains a specific number in Matlab

In this post, I am trying to solve the problem given in the comments of one of the old post.

Here's the problem, if I understand it correctly:

a =

     1     2     3     4     5

     2     3     4   -99     6

     3     4     5     6     7

     4   -99     6     7     8

     5     6     7     8     9

How to remove all the rows that contains the number -99, in this case, the row #2 and #4?

And here's the code I wrote to do this job:

[rows col]=size(a); %count the number of rows and columns of matrix a

j=0; %initialize a counter;

for i=1: rows

    if sum(a(i,:)~=-99)==col; %This determines if the row has -99 or not, if not, do nothing

    else     %shift all of the rest of the rows up one row

        for m=i: rows-1; 

        a(m,:)=a(m+1,:);

        end

        j=j+1; %count how many rows has -99, which equals how many times the rows has been shifted up 

    end

end

b=a((1:rows-j),:); %get rid of the last j rows


The result is:



b =


     1     2     3     4     5
     3     4     5     6     7
     5     6     7     8     9

I hope this can work for you, Winifred. Thanks for your comments!

Cell array, self-defined function, and save fig

I learned a lot of important things yesterday, after spend 10 hours in front of computer playing with MatLab. Alright, here's the code I came up with.


%Created on 6/30/2011
clear all
clc
sitenumber='01';


SampleLocation=[];
AER=[];
Err=[];




%% Importing data from intermediate file
filename='whatever it is.xlsx';
D1=xlsread(filename, 'A14:C25');
D2=xlsread(filename, 'I14:K25');
D3=xlsread(filename, 'Q14:S25');
D4=xlsread(filename, 'Y14:AA25');
D5=xlsread(filename, 'AG14:AI25');
D6=xlsread(filename, 'AO14:AQ25');
D7=xlsread(filename, 'AW14:AY25');
D8=xlsread(filename, 'BE14:BG25');
D9=xlsread(filename, 'BM14:BO25');
D10=xlsread(filename, 'BU14:BW25');
D11=xlsread(filename, 'CA14:CD25');
D12=xlsread(filename, 'CJ14:CL25');
D13=xlsread(filename, 'CR14:CT25');
D14=xlsread(filename, 'CZ14:DB25');
D15=xlsread(filename, 'DH14:DJ25');
D16=xlsread(filename, 'DP14:DR25');
D17=xlsread(filename, 'DX14:DZ25');
D18=xlsread(filename, 'EF14:EH25');
DCell={D1,D2,D3,D4,D5,D6,D7,D8,D9,D10,...
    D11,D12,D13,D14,D15,D16,D17,D18}; % Put all the arrays into one big cell array so that each time I can take one cell out and use it as the function input. 


% Use each array as function input % This is a self-defined function
for k=1:18
    [AERate Error]=getDecayrate(DCell{k}); %If use DCell (k), the function won't work.
    
    SampleLocation(1,k)=k;
    AER(1,k)=AERate;
    Err(1,k)=Error;
        
    newfilename=strcat('Site_', sitenumber, '_SampleLocation_', num2str(k),'.fig');
    saveas(gcf,newfilename) % This saveas function works pretty good. The .fig file can be edited later in MatLab.
end


 Result=[SampleLocation', AER', Err'];


%The following function calculates the first-order decay rate of the tracer gas, and returns two parameters. 

function [AER Err] = getDecayrate( location)
%UNTITLED2 Summary of this function goes here
%   Detailed explanation goes here


%AER=Data-1;
TimeS=zeros(1, length(location))';
LNC1=zeros(1, length(location))';
LNC2=zeros(1, length(location))';
for i=2 : length(location)
        TimeS(i)=(location(i,1)-location(1,1))*1440/60;
end


for j=2 : length(location)
    LNC1(j)=log(location(j,2)/location(1,2));
    LNC2(j)=log(location(j,3)/location(1,3));
end


slope1=sum(TimeS.*LNC1)/sum(TimeS.^2);
slope2=sum(TimeS.*LNC2)/sum(TimeS.^2);
AER=abs((slope1+slope2)/2);
Err=abs(AER-abs(slope1));
TimeModel=0:0.01:max(TimeS);
LNC1Model=TimeModel.*slope1;
LNC2Model=TimeModel.*slope2;
plot(TimeS, LNC1, 'xr',TimeS, LNC2, 'sb', TimeModel, LNC1Model,'r', TimeModel, LNC2Model, 'b', 'MarkerSize',10, 'LineWidth', 2)
title ('Location')
xlabel('Time (hours)')
ylabel('Ln(C/C0)')
end

simple data matching by using dataset arrays

Task : There are two Excel files, one contains the sample number and the time of sampling while the other contains the analysis results of each sample. Because the samples were taken in a chronicle order and were analysed in random order, it is kind of time consuming to manually find out each sample's result and put them into one file, especially when dealing with thousands of samples.

Here's a short code I wrote to do this:

% This program search the bag numbers and put the corresponding
% concentration values into the data file.
%% initialization
clear all;
clc;


%% import data
dataf=dataset('xlsfile','back.xls'); %aisle files from field test
concf=dataset('xlsfile','concentration.xls'); %concentration readings from autoTrac


%% determine dataset array size
datafL=length(dataf);
concfL=length(concf);


%% search and match
for i=1 : datafL
 for j= 1 : concfL-1
     
               if (  char(dataf.BagNumber(i))==char(concf.BagNumber(j))  )
                            dataf.Concentration1(i)=concf.Concentration(j);
                            dataf.Concentration2(i)=concf.Concentration(j+1);
                             break
               end
 end
end


%% Output data
export(dataf, 'xlsfile', 'Processed bag files-back.xls')

The dataset array is very power at handling different type of data, including numbers, strings, and even matrix.
To write a dataset array to an Excel file, I need to use export function instead of xlswrite.