NCL官方绘图手册：v1.3版，适用于数据可视化与分析

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NCL官方提供的绘图手册是一份详细的指南，专为NCAR Command Language (NCL) 用户设计，特别是针对那些希望访问、分析和可视化数据的专业人士。NCL是一款开源且免费的解释型编程语言，其版本为6.0.0，发布于2011年3月。它具有现代编程语言的许多通用特性，如类型系统、变量、运算符、表达式、条件语句、循环以及函数和过程等。该手册的重点在于提供迷你参考手册，帮助用户掌握基本的NCL语言特性。通过下载链接，学习者可以获取关于如何设置NCL环境的指导，包括高级图形界面的使用、颜色管理、向量绘制、等高线图、工作站配置、页面最大化以及地图绘制等内容。这本手册旨在让新用户快速上手，并为经验丰富的开发者提供深入的参考资料。手册的作者包括Sylvia Murphy、Mary Haley和Dennis Shea，他们鼓励读者对手册内容提出反馈，可以通过电子邮件ncl-talk@ucar.edu与他们交流。为了获取实际的脚本示例和样本图，手册还推荐访问以下两个网站：http://www.ncl.ucar.edu/Applications/ 和 http://www.ncl.ucar.edu/Document/Manuals/Getting_Started/，这两个站点提供了丰富的实践教程和案例研究，可以帮助用户在实践中理解和应用NCL进行数据分析和可视化。手册中的"courier-bold-built-in functions courier"部分可能是指文档中使用的一种特定字体或者强调了内置函数的重要性，这些内置函数是NCL编程中的核心组成部分，它们可以直接调用以实现各种计算和绘图操作。通过熟练掌握这些函数，用户能够更高效地完成复杂的任务，提升NCL编程的效率。 NCL官方绘图手册是一个全面的资源，无论是初次接触NCL的新手还是已有一定经验的开发者，都能从中找到所需的信息，从而充分利用NCL的强大功能进行数据处理和可视化。

Section 3.3 Running NCL

NCL can be run in two modes, script mode and interactive mode. To initiate the latter, simply type

"ncl" at the prompt. In interactive mode you are required to type each command separately. In

script mode, you create a separate NCL script which you send to the interpreter via the following

commands:

prompt> ncl [space] script

There is no required extension for an ncl script, but by convention the suffix "*.ncl" is used. NCL

scripts can have a begin and end statement, with a carriage return after the end statement. You

can optionally include options and command line arguments when you run NCL. See the Mini-

Reference Manual, whose location is mentioned on the first page of this document.

Section 4: Workstations

Opening a workstation is required prior to the creation of one or more plots. The workstation is

simply the location where the graphical instructions are sent (e.g. to a window or postscript file).

The workstation is given a name. This name becomes part of the output filename or title of X11

window. Users may have many workstations opened at the same time, although most only open

one. Only one colormap can be associated with each workstation.

There are six types of workstations: ncgm (NCAR computer graphics metafile), ps (postscript),

eps (encapsulated postscript, contains a bounding box), epsi (encapsulated postscript with a

bitmap preview), pdf, and X11 window. Examples:

wks = gsn_open_wks(“pdf”,”34_x_45”)

wks_2 = gsn_open_wks(“ps”,”myfile”)

The text to the left of the equal sign is a variable and can therefore be arbitrarily named.

Section 5: Plot Mods via Resources

Resources are the means by which we modify the default NCL plot. They may be strings, floats,

integers, doubles, etc. depending on the type of resource. The first two (or three) letters are lower

case, and the remaining letters are words of which the first letter is capitalized (e.g. cnFillOn).

If the resource is expecting a float value, an F is appended to the resource name (e.g.

txFontHeightF, mpMinLatF etc).

Section 5.1 Resource types

The first two letters of a resource identify what type of resource it is:

The

complet

e list of

resourc

under

these

categori

es may be accessed at:

http://www.ncl.ucar.edu/Document/Graphics/Resources/

Additionally, there is a unique set of gsn resources that were created specifically for the gsn

interfaces, and these resources can be found at the above URL as well.

Section 5.2 Setting resources

Resources are passed to the high-level graphpical interfaces as attributes to a logical variable.

Attributes are assigned using the @ symbol. Note that res is a user-defined variable. It is wise to

create separate variables for resources to be passed to different types of interfaces (e.g. con_res,

vec_res, xy_res). Vector resources sent to a contour routine will cause warning messages. The

following code snippet creates the variable res which is of type logical. Attributes associated with

res are then assigned.

res = True

res@tiMainString = “my title”

res@cnFillOn = True

The resource variable is always the last argument in the graphical interface calling sequence.

plot = gsn_csm_contour(wks,data,res)

plot2 = gsn_xy(wks,data,res)

The variable to the left of the equal sign is of type graphic. The name is arbitrary.

Section 5.3 Some common resources

It is impossible in the space provided here to give a complete description of each resource and its

options. Appendix A contains a list of some of the most commonly used resources.

Section 5.4 Drawing a plot and gsnDraw

By default, the high-level graphical interfaces create and draw graphical objects. This behavior

can be changed by setting the resource gsnDraw = False.

Section 5.5 Advancing the frame and gsnFrame

By default, the high-level graphical interfaces advance the frame after the graphical object has

been drawn. One analogy for the frame is that of a page in a book. The workstation is the book,

and advancing the frame is equivalent of turning the page in the book. A book or workstation can

annotation manager

plot manager

vector field

contour

primitive

vectors

coordinate arrays

scalar field

viewport

graphical style

title

workstation

labelbar

tickmarks

workspace

legend

text

xy plot

maps

transform

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