China PM2.5 & PM10 historical data repository

http://pan.baidu.com/s/1dD8KdpB

More data will be added to this repository in the future.

Set the properties of a dataset array in Matlab

The percent sign, %, can be used in the matlab code to add explanatory information to the code. Similarly, we can add explanatory information to a dataset array, by using the dataset array properties. The set function can be used to assign values to the dataset property, and the get function can be used to access these information.

DS=dataset(...) % a dataset array is constructed

DS=set(DS, 'Description', 'Whatever can describe the dataset can be put here');

get(DS) % show dataset array properties

summary(DS) % also show dataset array properties 

The 'Description' can be replaced with other properties which are displayed by the get function. 

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)

How to concatenate two datasets in Matlab?

I wanted to vertically combine two datasets, so I can keep a long file of all the test results. The join function does not work here anymore. Of course this is even not a problem in Excel. However, to make it work in Matlab, it did took me a while to figure it out.

c=cat(1, a, b)

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.