SCILAB Programming

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SCILAB Programming

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Simple Calculation

->1+1

ans = 2.

-->x = 5; -->X = 50;

-->y = 6; -->z = 8 z = 8.

-->m = x*y*z m = 240.

SCILAB is case sensitive.

(3)

Vector and Matrix

->a = [1 2 3]

a = 1. 2. 3.

->b = [1; 2; 3]

b = 1.

2.

3.

--> x=[1 2;3 4];

-->y=[5 6;7 8];

-->x+y ans =

6. 8.

10. 12.

-->c = [1 2; 3 4]; --> inv(c)

ans = - 2. 1

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Matrix: Referring to Rows, Columns, Elements

-->c = [1 2; 3 4]

c = 1. 2.

3. 4.

-->c(1,2) ans = 2.

--> c(2,2) = 8;

--> c

c = 1. 2.

3. 8.

--> c(1,:)

ans = 1. 2.

--> c(:,1)

ans = 1. 3.

--> c = [10 9 8 7 6 5; 1 2 3 4 5 6];

--> c(1,2:4) ans =

9. 8. 7.

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Two Ways of Matrix Multiplication

-->x = [1 2; 3 4]

-->x*x ans = 7. 10.

15. 22.

-->x.*x ans =

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Statistic Commands

-->a=[1 2];

-->sum(a) ans = 3

-->mean(a) ans = 1.5 -->stdev(a)

ans = 0.7071068 -->variance(a)

ans = 0.5

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Graph Plotting

x = [1 2 -1 3 7];

clf;

plot(x);

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Graph Plotting

--> x = [1 2 3 4 5 6];

--> y = x.^2;

y = 1. 4. 9. 16. 25. 36.

--> clf;

--> plot(x,y)

“.” is for each element’

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3-D Graph Plotting

x = [1 2];

y = [1 2];

z = [3 5; 4 6];

clf;

plot3d(x,y,z);

3.0 3.5 4.0 4.5 5.0 5.5 6.0

Z

1.2 1.0 1.6 1.4

2.0 1.8

X

1.0 1.2 1.4 1.6 1.8 2.0

Y

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Clear and Comment

--> x = 1;

--> x x=1.

-->clear;

-->x

!--error 4

undefined variable : x

x = 1; // I want to set x equal to 1.

(11)

Loop Command: For (1)

for index = start : end do something

end

//display 1, 2, .. 10 for i = 1 : 10

//1 + 2 + 3 .. 99 = ? s = 0;

for i = 1 : 99

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Loop Command: For (2)

for index = start : increment : end do something

end

//1 + 3 + 5.. 99 = ? s = 0;

for i = 1 : 2 : 99 s = s + i;

end

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Solow Model’s Simulation

clear;

alpha=0.5; s=0.1; d=0.1;

k(1)=0.6;

for t=1:1000

y(t) = k(t)^alpha;

i(t) = s*y(t);

c(t) = (1-s)*y(t);

k(t+1) = (1-d)*k(t) + i(t); ⁰ ¹⁰⁰ ²⁰⁰ ³⁰⁰ ⁴⁰⁰ ⁵⁰⁰ ⁶⁰⁰ ⁷⁰⁰ ⁸⁰⁰ ⁹⁰⁰ ¹⁰⁰⁰

0.75 0.80 0.85 0.90 0.95 1.00

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Utility Plot

clear;

for i=1:10 x(i)=i;

y(i)=i;

end

for i = 1:10 for j = 1:10

z(i,j) = x(i)*y(j);

w(i,j) = 40;

end end clf;

plot3d(x,y,z);

plot3d(x,y,w);

0 20 40 60 80 100

Z

1 4 7

10 X

1 2 3 4 5 6 7 8 9 10

Y

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Conditional Command: if then

if logical-statement then do something

end

x = 0;

if x < 1 then x = 1;

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Conditional Command: if then else

if logical-statement then do something

else

do another thing end

x = 3;

if x < 1 then x = 1;

else

x = 2;

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Logical Comparison

• Is x equal y? x == y

• Is x more than y? x > y

• Is x more than or equal y? x >= y

• Is x > 10 and < 100? x > 10 & x < 100

• Is x > 10 or < 100? x > 10 | x < 100

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Solow Model with technology shock

clear;

alpha=0.5; s=0.1; d=0.1; k(1)=0.1; a = 1;

for t=1:1:1000 if t == 500 then

a = 1.1;

end;

y(t) = a*k(t)^alpha;

i(t) = s*y(t);

c(t) = (1-s)*y(t);

k(t+1) = (1-d)*k(t) + i(t);

end plot(y);

0 100 200 300 400 500 600 700 800 900 1000 0.3

0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3

(19)

Your own function

function r=functionname(input1, input2, …) calculating r

endfunction

function r=consumption(y, a, b) r = a + b*y;

endfunction

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Variable inside and outside function.

Function can see the value of variable outside it but cannot change its value

function r=test() r = y + 10;

y = 8;

endfunction y = 5;

test() --> 15 y

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Conditional Loop: While

while conditional_statement do_something

end

i = 1;

while i < 10

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Conditional Loop: While

//Find the maximum x such that 1+2+3+4+…+x < 2000 s = 0;

i=0;

while s < 2000 i=i+1;

s = s+i;

end i-1

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Conditional Exit from Loop: Break

i = 1;

while i < 10 disp(i);

if i==3 then break;

end

for i=1:10 disp(i);

if i==3 then break;

end end

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Scilab Help

• Scilab help can be accessed by [F1].