Flow Charts and Graphs

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Flow Charts and Graphs

Introduction

When you have lot of raw data and many things are depending on that data, it becomes very difficult to take decisions just based on that. On the other hand, if you represent the same data in graphical manner, it becomes very easy to read and analyze it. Graphical representation of data gives viewer a clear-cut idea of the data from every aspect. Similarly, if there are many inter-related decisions you have to take based on the data, flow charts come to rescue. Decision making becomes easy with the use of flow charts. It also helps you to know what you should do after each step or where it is leading. As per the saying, ‘A picture is worth a thousand words’, flow charts and graphs give you a nice, pictorial view of your data. Those are important tools for taking management decisions.

Objective

In this chapter, we are going to learn the importance of flow charts and graphs in engineering drawing. We will study what is a flow chart, symbols used in it, how to draw flow charts and straight line diagrams. We will also study how and where we can use it. We will learn about different types of graphs and will learn to draw it.

Flow chart

Flow chart is a drawing tool which helps in decision making. It provides a way to solve complicated things, so, one can plan actions accordingly. Its effectiveness depends on the way people use it. Flow charts also help you to understand the process and help you to think where improvement is needed. It gives you step-by-step pictorial representation of the process. It can be used to define the process, analyze the process, and standardize the process.

Types of Flow Charts:

Two main types of flow chart are: i) Basic Flow Charts ii) Straight Line Diagrams (SLD).

Basic Flow Charts need Symbols, SLD do not necessarily need symbols. SLDs can be used for depicting Flow Diagrams.

Benefits of flow Chart:

1. A sequential, precise and short description of a process can be obtained.

2. Chances to overlook or miss any step, input-output elements are reduced.

3. Misuse of elements or tools can be located precisely.4. Areas of improvement can be identified easily.

Symbols used in flow charts

Since flow chart is a graphical or symbolic representation of a process, each step in the process is represented by a different symbol. It also contains a short description of the process step. These symbols are linked to each other with arrows showing the process flow direction. Some basic symbols used in flow chart are discussed here:

Terminators: These are represented as rounded rectangles located in the beginning of the process and end of the process. You might see words ‘Finish’ or ‘Submit query’ or ‘Receive product’ which also indicate end of the process instead of word, ‘End’.

Process: Represented as a rectangular shape indicating normal process.

Decision: Decision or condition in flowchart is represented as a diamond shape. It generally contains ‘Yes/No’ or ‘True/False’ question. This diamond will have two arrows coming out of it. One of the arrows will go to ‘Yes’ or ‘True’ and one will go to ‘No’ or ‘False’.

Input / Output: Data Input / Output for the process is represented as parallelograms.

Arrows: Arrows coming from one symbol and ending to another indicates the direction of the flow.

To understand the meaning of all the symbols we have learned; let’s use the flow chart to define a simple process. Let’s say, the process is ‘Preparation of tomato sauce’. Following steps are there in the process: Clean the tomatoes, cook them in pressure cooker, make a pulp in mixer, remove seeds and wastage, add spices and cook the mixture on stove to remove water, check the quality and then pack the tomato sauce.

Fig. 1 – Flow chart of a simple process

Start

Cleaning of tomatoes

Cooking of tomatoes in pressure cooker

Grinding cooked tomatoes in mixer

Cooking the mixture over stove to remove excess

Quality check

Packing

End

Remove seeds and peels from the pulp

Add spices to the mixture

Reject/Discard

No

Yes

SLD - Straight Line Diagram

Straight Line Diagrams are graphical liner presentations of Information. With the help of relevant textual information (such as tags, names) one can use only straight lines to represent a simple or complex information.

A good example of a generic SLD is route maps shown in Locals and Metros. Following is one example:

Fig. 2 – Route map of Delhi Metro

(Curtsy: Delhi Metro)

A straight line diagram can also be used to indicate internals of a building, such as a workshop, where one can depict what tools are kept where. Also, SLD for electrical circuit of a given building is another possibility. Electrical Services, Telecommunication Services and Civil Engineering Services are the major sections where SLD are utilized. As a whole, SLDs are a great tool for depicting complex diagrams such as town planning, Pipe Line Plans, Electrical Circuits in a building or across a city, without worrying about the details of each small object/tool/system in the plan.

Graph

A graph is a chart or drawing displaying the relationship between numbers or amounts or quantities. It is also defined as Visual representation of statistical information with the help of two or more reference axes. In such drawings, lines, bars or proportional area represent how one quantity is dependent on another quantity. Graphs help us to understand the relation between two different quantities. These quantities are called as ‘Data’. Graphs are widely used in the field of mathematics, statistics, science, education etc.

Steps to plot a graph –

1. Draw two axes, namely, X as horizontal axis and Y as vertical axis, both at right angled to each other. The point of intersection of axes is called the 'Origin' of the scale. It is treated as the 'Zero' of the scales.

2. Decide a scale - measure the maximum available units on any one axis of the graph. Name it as (A), find the maximum amount to be plotted along that axis. Name it as (B), the division of A by B gives the scale along that particular axis. e.g. if maximum available units along X axis are 12 cm (A) and maximum 24 months' (B) record is to be plotted along X axis then A/B = 12/24 = 1:2. That is, every 1 cm along the X axis represents 2 months or for representing each month, 0.5 cm of X axis can be used. Similar procedure is followed for other axes.

3. To plot each point of the graph, the X and Y values of that particular information are measured along the respective axes. The point of intersection of perpendiculars drawn from these values represents the point of information.

There are different types of graphs which can be used for different reasons. We will see few of them in this chapter.

Types of Graph:

1. Line Graph

These types of graphs are the most commonly used graphs. These are very simple to draw and easy to understand. A line graph shows points plotted on a graph. The points are then connected to form a line. The following line graph (Fig. 3) shows runs made by two Cricket teams, A and B in various overs. It is usually used to display each single data value. The graph shows us progress made by both the teams.

Overs First Fifth Tenth Fifteenth Twentieth

Runs made by Team A 60 120 185 240 300

Runs made by Team B 80 140 170 241 323

Fig. 3 – Line graph

2. Bar Graph

It is also called as column graph. A bar graph uses bars or columns to show data. The bars are of two types: vertical (up and down), or horizontal (across). These graphs are easy to understand because they are presented in the form of rectangular bars with different height according to its value. The data can be in words or numbers.

0

50

100

150

200

250

300

350

First Fifth Tenth Fifteenth Tw entieth

The following bar graph (Fig. 4) shows comparative temperature of different cities in India.

City Mumbai Delhi Kalikat Chennai Nagpur Bengaluru

Temp.

In 0C35 40 36 39 42 28

Fig. 4 – Bar graph

3. Pie Graph

It is shaped like a circle divided into pieces like pieces of pie and so the name Pie graph. It is normally called Pie chart. Different pieces or segments show the percentage of specific data. A pie chart displays how much each value contributes to the total. If you have few figures or quantities to compare, pie chart is a good option to represent. But with too many quantities, pie chart looks very messy.The following pie chart (Fig. 5) shows number of employees working in different departments of a workshop. It shows comparative strength of each department.

Department

Weldin

g

Fittin

g

Turnin

g

Carpentr

y

No. of

employees 40 37 46 20

0

5

10

15

20

25

30

35

40

45

Mumbai Delhi Kalikat Channai Nagpur Bangaluru

Fig. 5 – Pie graph

Benefits of Graph: Graphs show relationship between two quantities in visual form. And

due to its visual form, it is easy to read. Graph is very useful management tool to analyze information. By using different colors in your graph, you can emphasize important

points. By using different software, different style of graphs can be drawn,

they can be enhanced by adding legends, labels etc. This way is more powerful than just a talk.

Summary

Here is the summary of what we learned in this chapter: Flow charts and graphs are very important drawing tools. Flow charts give step-by-step pictorial information of the process. It helps in decision making process. In flow charts, each step in the process is represented by a symbol. Graph shows relationship between two quantities. It helps you to analyze the data easily. We learned three different types of graphs: line graph, bar graph and

pie graph.

Activity

Welding, 40

Turning, 46

Fitting, 37

Carpentry, 20

1. Draw a Straight Line Diagram (SLD) for the procedure of welding two MS circular rods of 20 mm diameter at right angles to each other.

2. Draw a flow chart for following procedure.20 students in class 10th appeared for one test. The test was of 100 marks. Passing marks were 50. If the student has got marks more than 90, he/she will get ‘Excellent’ grade. Other students will get ‘Satisfactory’ grade.

3. Plot a bar graph of following information:

Students Anuja Rahul Meghana Hari

Marks 31 90 78 57

4. Plot a line graph of a 20-20 cricket match performance, given as follows:

Over Firs

t

Fifth Tent

h

Fifteenth Twentieth

Runs by Team A 12 34 120 190 230

Runs by Team B 3 60 85 100 236

5. Read the following graph and answer the questions

1) What is the weight of chicks after 6 weeks?

weight gain

0

500

1000

1500

2000

2500

1 2 3 4 5 6 7 8

week

wei

gh

t in

gm

s

Series1

Series2

2) What is the weight of chick after 3 weeks? 3) What conclusion you can draw from the graph?

6. Try to draw graphs and flow charts of above given examples with the use of software like Microsoft Excel (for graphs). You can explore this further with the use of Internet.

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