coursera机器学习课后习题答案全套

=============================================================================== = JSONLab = = An open-source MATLAB/Octave JSON encoder and decoder = =============================================================================== *Copyright (C) 2011-2015 Qianqian Fang <fangq at nmr.mgh.harvard.edu> *License: BSD License, see License_BSD.txt for details *Version: 1.0 (Optimus - Final) ------------------------------------------------------------------------------- Table of Content: I. Introduction II. Installation III.Using JSONLab IV. Known Issues and TODOs V. Contribution and feedback ------------------------------------------------------------------------------- I. Introduction JSON ([http://www.json.org/ JavaScript Object Notation]) is a highly portable, human-readable and "[http://en.wikipedia.org/wiki/JSON fat-free]" text format to represent complex and hierarchical data. It is as powerful as [http://en.wikipedia.org/wiki/XML XML], but less verbose. JSON format is widely used for data-exchange in applications, and is essential for the wild success of [http://en.wikipedia.org/wiki/Ajax_(programming) Ajax] and [http://en.wikipedia.org/wiki/Web_2.0 Web2.0]. UBJSON (Universal Binary JSON) is a binary JSON format, specifically optimized for compact file size and better performance while keeping the semantics as simple as the text-based JSON format. Using the UBJSON format allows to wrap complex binary data in a flexible and extensible structure, making it possible to process complex and large dataset without accuracy loss due to text conversions. We envision that both JSON and its binary version will serve as part of the mainstream data-exchange formats for scientific research in the future. It will provide the flexibility and generality achieved by other popular general-purpose file specifications, such as [http://www.hdfgroup.org/HDF5/whatishdf5.html HDF5], with significantly reduced complexity and enhanced performance. JSONLab is a free and open-source implementation of a JSON/UBJSON encoder and a decoder in the native MATLAB language. It can be used to convert a MATLAB data structure (array, struct, cell, struct array and cell array) into JSON/UBJSON formatted strings, or to decode a JSON/UBJSON file into MATLAB data structure. JSONLab supports both MATLAB and [http://www.gnu.org/software/octave/ GNU Octave] (a free MATLAB clone). ------------------------------------------------------------------------------- II. Installation The installation of JSONLab is no different than any other simple MATLAB toolbox. You only need to download/unzip the JSONLab package to a folder, and add the folder's path to MATLAB/Octave's path list by using the following command: addpath('/path/to/jsonlab'); If you want to add this path permanently, you need to type "pathtool", browse to the jsonlab root folder and add to the list, then click "Save". Then, run "rehash" in MATLAB, and type "which loadjson", if you see an output, that means JSONLab is installed for MATLAB/Octave. ------------------------------------------------------------------------------- III.Using JSONLab JSONLab provides two functions, loadjson.m -- a MATLAB->JSON decoder, and savejson.m -- a MATLAB->JSON encoder, for the text-based JSON, and two equivallent functions -- loadubjson and saveubjson for the binary JSON. The detailed help info for the four functions can be found below: === loadjson.m === <pre> data=loadjson(fname,opt) or data=loadjson(fname,'param1',value1,'param2',value2,...) parse a JSON (JavaScript Object Notation) file or string authors:Qianqian Fang (fangq<at> nmr.mgh.harvard.edu) created on 2011/09/09, including previous works from Nedialko Krouchev: http://www.mathworks.com/matlabcentral/fileexchange/25713 created on 2009/11/02 Fran�ois Glineur: http://www.mathworks.com/matlabcentral/fileexchange/23393 created on 2009/03/22 Joel Feenstra: http://www.mathworks.com/matlabcentral/fileexchange/20565 created on 2008/07/03 $Id: loadjson.m 452 2014-11-22 16:43:33Z fangq $ input: fname: input file name, if fname contains "{}" or "[]", fname will be interpreted as a JSON string opt: a struct to store parsing options, opt can be replaced by a list of ('param',value) pairs - the param string is equivallent to a field in opt. opt can have the following fields (first in [.|.] is the default) opt.SimplifyCell [0|1]: if set to 1, loadjson will call cell2mat for each element of the JSON data, and group arrays based on the cell2mat rules. opt.FastArrayParser [1|0 or integer]: if set to 1, use a speed-optimized array parser when loading an array object. The fast array parser may collapse block arrays into a single large array similar to rules defined in cell2mat; 0 to use a legacy parser; if set to a larger-than-1 value, this option will specify the minimum dimension to enable the fast array parser. For example, if the input is a 3D array, setting FastArrayParser to 1 will return a 3D array; setting to 2 will return a cell array of 2D arrays; setting to 3 will return to a 2D cell array of 1D vectors; setting to 4 will return a 3D cell array. opt.ShowProgress [0|1]: if set to 1, loadjson displays a progress bar. output: dat: a cell array, where {...} blocks are converted into cell arrays, and [...] are converted to arrays examples: dat=loadjson('{"obj":{"string":"value","array":[1,2,3]}}') dat=loadjson(['examples' filesep 'example1.json']) dat=loadjson(['examples' filesep 'example1.json'],'SimplifyCell',1) </pre> === savejson.m === <pre> json=savejson(rootname,obj,filename) or json=savejson(rootname,obj,opt) json=savejson(rootname,obj,'param1',value1,'param2',value2,...) convert a MATLAB object (cell, struct or array) into a JSON (JavaScript Object Notation) string author: Qianqian Fang (fangq<at> nmr.mgh.harvard.edu) created on 2011/09/09 $Id: savejson.m 458 2014-12-19 22:17:17Z fangq $ input: rootname: the name of the root-object, when set to '', the root name is ignored, however, when opt.ForceRootName is set to 1 (see below), the MATLAB variable name will be used as the root name. obj: a MATLAB object (array, cell, cell array, struct, struct array). filename: a string for the file name to save the output JSON data. opt: a struct for additional options, ignore to use default values. opt can have the following fields (first in [.|.] is the default) opt.FileName [''|string]: a file name to save the output JSON data opt.FloatFormat ['%.10g'|string]: format to show each numeric element of a 1D/2D array; opt.ArrayIndent [1|0]: if 1, output explicit data array with precedent indentation; if 0, no indentation opt.ArrayToStruct[0|1]: when set to 0, savejson outputs 1D/2D array in JSON array format; if sets to 1, an array will be shown as a struct with fields "_ArrayType_", "_ArraySize_" and "_ArrayData_"; for sparse arrays, the non-zero elements will be saved to _ArrayData_ field in triplet-format i.e.